Walkthrough (Below Zero)

This page serves as a full-game survival mode walkthrough of Subnautica: Below Zero. It also contains gameplay tips and helpful pointers for successfully mastering the oceans. Keep in mind that this page will have spoilers, as it also summarizes the events as you follow along with the story. Note that if at any point in the playthrough you become unable to progress due to a bug, check Console Commands to see if any commands can help.

Background
You play as Robin Ayou, an employee for Xenoworx: An Alterra Initiative, who stealths her way onto the planet 4546B. Robin's mission is to investigate the death of her sister, Sam Ayou.

Intro Site
The story starts with Robin crashing in a stolen shuttle. After the intro cutscene, you gain control of Robin. You can use the    keys to walk,  to sprint, and move your mouse to look around. You will get a Databank Entry. The game instructs you to press to open the PDA in order to check the entry, which is an essential tool in Subnautica: Below Zero. There are some supplies on the ground; collect them. There should be 3 Filtered Water Bottles, 3 Nutrient Blocks, and 9 Flares. If you're having trouble finding everything, consider turning on the "Highlight interactable" setting in the options menu, under Accessibility. While exploring outside the water you should pay attention to your body heat. If hypothermia becomes imminent, you can warm yourself up with the help of Thermal Lilies or the burning wreckage of your shuttle. You can cross a path to an open water area from which you can swim to the Drop Pod.

Stranded
The path exits into the main area of gameplay, known as Sector Zero. The exact biome you are now in is the Shallow Twisty Bridges. At this point, your food bar should be at about half. Food and water are two core gameplay threats that need to be managed constantly. To refill food and water, Robin must eat cooked fish, which can be made using caught fish at a Fabricator, eat Cured Fish, which are made from fish and Salt Deposits, and drink Filtered Water, which can be crafted using Bladderfish. Also present is the health bar, which monitors how much damage you can take before dying. Damage usually comes from predatory fauna or flora, though it can also be caused by fall damage and excessive heat. Healing requires the use of First Aid Kits, but health will also slowly regenerate if you've refilled your food and water meters enough. Finally, the last two indicators are Oxygen and Temperature. Oxygen slowly runs out at a pace of 1 unit per second (unless your depth is below 100 meters and you don't have a Rebreather equipped) when underwater and in bases/vehicles without power. Temperature, on the other hand, decreases when outside of water and in cold environments. Note that the speed at which temperature decreases depends on the biome and the current weather.

Shortly after exiting the path, Robin arrives at the Drop Pod, a safe location for Robin to store and craft items. Inside the Drop Pod is a 6&times;8 storage locker and a Fabricator, one of the most essential crafting machines in the game. The Fabricator has four tabs: Resources, for crafting items that are used to craft final products; Sustenance, for crafting food and water; Personal, for crafting Equipment and Tools; and Deployables, useful items that are placed into the world and have a handy effect. Right now, there are three items of vital importance to craft: the Survival Knife, the Scanner, and the Standard O₂ Tank.

Important Tools
The quickest tool to craft is the Scanner. Its recipe is one Battery and one Titanium. Titanium can be acquired by breaking open Limestone Outcrops, which litter the floor and walls of many biomes, including the one you are currently in. The outcrops also drop Copper Ore, which is required to craft batteries. The other resources needed for batteries are two Ribbon Plants, which are small, narrow, yellow and green plants generally found in the caves of the Shallow Twisty Bridges. Once you have all the items you need, return to the Drop Pod to craft the Scanner. The Scanner allows you to scan fauna, flora, rocks, and most importantly, Fragments. Fragments are broken pieces of technology that litter the floors of many biomes. Each biome has a different array of fragments. One very useful piece of technology that can be scanned in the Shallow Twisty Bridges is the Seaglide, which greatly increases your movement speed. Note that it and the Scanner require a charged battery to operate. If your tool runs out of power, simply craft another battery and replace it by pressing while holding the tool. Later on in the game you'll be able to create a Battery Charger and place it in your base to recharge the batteries you have.

The next important item is the Survival Knife. The knife allows you to collect certain resources and fight off aggressive life forms should the need arise. The knife's recipe is one Titanium and one Silicone Rubber. Silicone Rubber can be crafted by harvesting a Seed Cluster in the Arctic Kelp Forest. One of the forests can be found in the direction away from the tunnel. Once you make your way there, the seed clusters are bright red bulbs hanging off the tall Creepvines, which resemble real-life kelp. It is prudent to harvest as many as you can carry, as you will need more later. Once you have everything you need, head back to the Drop Pod to fabricate the knife.

The third item that is necessary to craft is the Standard O₂ Tank. The tank increases your total oxygen, allowing you to stay underwater much longer. Its crafting recipe is two Titanium and a Fiber Mesh. Fiber Mesh is crafted using two Creepvine Samples, which can be acquired by using the Survival Knife on a Creepvine in the Arctic Kelp Forest. To use the knife, simply equip it using the number keys and then click. Once you craft the tank back at the Drop Pod, several more crafting recipes will be unlocked.

While not strictly necessary, there are some other tools you can craft. One is the Flashlight, and the other is the Air Bladder. The Flashlight simply requires a Battery and Glass. The Flashlight can help you search for materials in the dark, as the world can be very poorly lit in certain places, especially around night. Glass is crafted by combining two Quartz. You may have already seen quartz; it is a white, crystalline object found on the floors of the Shallow Twisty Bridges. The Air Bladder requires Silicone Rubber and a Bladderfish, and can be used in two different ways. The first way is by replenishing your oxygen meter with 10 seconds of air. The other, more useful way is by allowing Robin to rapidly ascend 100 meters from the ocean floor to the water surface. The speed at which the player ascends is faster than most predators, making this a useful escape tool while in a pinch.

Supplies
After heading west of the Drop Pod, towards the Sparse Arctic and the Arctic Kelp Forests, the PDA locates an emergency supply cache in the Arctic Kelp Forest and adds the beacon to Robin's PDA. The supply cache contains the blueprint for the Compass, which puts a compass on the player's HUD. Additionally, the player can find a PDA with a conversation between Fred Lachance and Sam Ayou. The beacon for the cache can be turned off in the beacons tab of the PDA or taken to be placed in another point of interest. Something you should take the time to craft is the High Capacity O₂ Tank, an upgraded version of the Standard O₂ Tank you previously crafted. Though not absolutely necessary to progress, if you are an inexperienced player it is recommended to craft this upgrade. The blueprint for it can be found in the Twisty Bridges; just explore until you find it, or skip to the next section if you can go without. Its recipe calls for four Titanium, two Glass, and one Silver Ore. In total, you need four quartz for the tank. Silver ore is more tricky to find; it is available in the Arctic Kelp Caves and the Twisty Bridges. The former is safer, as it has no predators, but can be easy to get lost in. It is also significantly easier to find the Twisty Bridges, as they are just trenches surrounded by some parts of the Shallow Twisty Bridges, whereas Arctic Kelp Caves entrances are few. Whichever you decide, you must look for Argentite Outcrops, which are grey rocks protruding from the surface of walls. Once you have everything you need, head back to the Drop Pod to craft the tank. Remember to take off your old tank in order to craft the new one.

Finding the Sanctuary
If you explore the Twisty Bridges, you will receive an SOS signal originating from the sanctuary. The sanctuary is located deep in the biome, at a depth of 180m. You can find the entrance by going farther away from the Drop Pod, opposite the direction the area of Robin's crashed shuttle. Once you get near the sanctuary, you may see some alien pillars. Follow the pillars to find the sanctuary, which is another large alien structure with a wide, square facade. Going through the opening will take you out of the water and back onto your feet.

The Download
The first thing in front of you is the cave of the sanctuary. The entrance to the inner sanctuary contains three Ion Cubes, which you may want to pick up as they are not very common. Be sure not to waste them as they will be required to progress, though more can be found around Sector Zero. Follow the rocky path to get to the inner sanctuary, which is marked by more alien structures. Inside the inner sanctuary is a large, open room with a giant cube-like structure in the center. Along the way, you'll get a message telling you the facility's power is low. An alien, disembodied voice speaks to Robin and says it is running out of time. The facility tells Robin that "a storage capacity is found on her person". Go around the cube and up the ramp to find a green hologram. Interacting with the hologram initiates a cutscene in which an Architect consciousness is downloaded into Robin's brain. Once Robin regains consciousness, she and the alien talk to each other and Robin becomes upset about what happened. The alien becomes silent while it thinks of a solution for their current situation. Finally, the Sanctuary Cube collapses. You can now exit the sanctuary.

The Delta Island
After Robin exits the Sanctuary, the Architect's voice tells her it needs a body to transfer itself into. The voice tells her it belongs to a species called the Architects. Robin asks for its name, so it tells her she may append her seed code to his species designation. The voice concedes that Robin may call it Al-An. After this exchange, the next step in the story is to head to the Delta Island, an island in the center of Sector Zero that holds the Communications Tower, a large installation to monitor activity in Sector Zero. Head towards the island, which can be seen from a fair distance to the South (away from the tunnel and mountains).

When you get to the island, you must then climb it towards the top where the tower resides. Go through the caves to reach it. It is at this point that the player will most likely face the dangers of hypothermia for the first time. On the Delta Island, Thermal Lilies provide a very convenient source of heat that makes surviving the island very easy. On her way to the top, Robin will trigger a cutscene involving Marguerit Maida, who tells her to stay off her land and then leaves in her modified Prawn Suit. Your PDA will mark a beacon showing her last tracked position. Remember it for later.

Delta Station
Once at the top of the island, you will most likely see Delta Station before seeing the tower. By the base is a fragment of Habitat Builder. The habitat builder allows Robin to build Seabases in the water or on land. Seabases allow you to have a base away from the Drop Pod, which can contain storage and useful facilities such as a Fabricator. See Seabases and Hull Integrity for more information.

There are also certain scannable objects in the base. Most do not have a use other than vanity, however two specific objects stick out as extremely useful; the Multipurpose Room and the Modification Station. The room can be scanned from the outside (it is the large round room, there are two of them), and the Modification Station is found inside the bedroom of the base. It can be used to build upgrades to certain equipment and tools, such as the knife and the oxygen tank. After scanning everything you need or want, exit the base and head up the stairs in front of you to the radio tower. It is also revealed that the Delta Station quartered the following members: Fred Lachance, Jeremiah Murgle, and Emmanuel Desjardins.

Communications Tower
At the very peak of the island, Robin can walk up the Communications Tower. There are a couple of PDAs nearby, most of which were abandoned by Jeremiah Murgle. A terminal can be found in front the tower's ladder. When Robin interacts with the terminal for the first time, she will receive a status report revealing that the area is under active satellite surveillance.

Seatruck
At this point, the story will force you into deeper sections of the region. It is highly recommended to acquire the Seatruck, a submarine that can be modified to suit your needs using attachable and detachable modules. The first step is finding its Fragments, which can be found in the Twisty Bridges and Thermal Spires. They are more easily located in the Thermal Spires, the biome immediately surrounding the Delta Island. Once you scan three pieces, you'll unlock the Seatruck; however, you also need the Mobile Vehicle Bay, which allows you to build vehicles. These fragments (you need three) can be found in the Twisty Bridges as well, however they are more common in the Arctic Kelp Caves, which are large caves whose entrances are in the Arctic Kelp Forest. Be prudent when diving here; Sea Monkeys can steal your held item, and it may be difficult to find your way out.

Once you have both blueprints, it's time to craft both. The Mobile Vehicle Bay calls for one Titanium Ingot, one Lubricant, and one Power Cell. All three are easily crafted; the Titanium Ingot simply requires five Titanium, and the Power Cell needs two Batteries and a Silicone Rubber, which you have crafted before. Once you've crafted the bay, simply equip it and drop it in somewhat deep water and it'll float to the surface and open. Climb on by clicking it and click again to open the crafting menu.

Next, you need to craft the Seatruck itself, which is more difficult to acquire the ingredients for. It calls for another Titanium Ingot, one Advanced Wiring Kit, two Glass, three Lead, and one Power Cell. Titanium Ingots and Glass are simple; the rest, however, should be new to you. The Power Cell requires two batteries and one silicone rubber. Advanced Wiring Kits require a Wiring Kit (which requires two Silver Ore), two Gold, and a Computer Chip each. Most of these you've seen before; they can be found from nodes all over the region. Table Coral Samples, however, are quite rare. They can be found by cutting Table Corals, which are flat corals found in the Twisty Bridges. They are rare, so keep looking, and pay special attention to the walls of the biome. After you manage to find those, you need Lead. They can be found quite easily from Galena Outcrops in the Thermal Spires and Twisty Bridges. As usual, the former is more reliable.

Once you've managed to get all the materials needed to craft the Seatruck, head back to your Mobile Vehicle Bay, or drop it back down if you picked it up. Climb on and craft the Seatruck. After a short animation, it'll be dropped in the water in front of you. You can enter it through a hatch on the roof. The Seatruck runs on Power Cells, which need to be charged up in Power Cell Chargers; alternatively, you can build a Moonpool to charge your Seatruck while docked. The Seatruck is controlled much in the same way as the player; mouse to look around, to move. Pressing backward will also turn on a rearview mirror, which can be disabled by pressing forward again. The main feature of the Sea Truck is modularity; using Seatruck modules, you can pick and choose what your Seatruck can do, from storage to teleportation. It is also upgradeable using upgrades crafted in the Seatruck Fabricator Module. The modules and upgrades must both be unlocked through more exploration, though some upgrades are unlocked by default. See the Seatruck page for more information on modules and upgrades.

Seatruck Upgrades
The next section requires bringing your Seatruck to depths under 200 meters; however, the Seatruck can't go any lower than that yet. To improve its crush depth, you must build the Seatruck Fabricator Module. Its fragments are located beneath the Twisty Bridges in a dark cave biome called the Deep Twisty Bridges. The entrance is located at the floor of the Twisty Bridges, near Sanctuary Zero. You can leave your Seatruck parked just above its crush depth and swim down to scan the fragments. Make sure to bring a form of light, and do your best to avoid the Squidsharks. While down there, you may also want to scan fragments for the Seatruck Storage Module, however you do not need them to progress.

Once you have the blueprint, you need to craft the Fabricator Module. All Seatruck modules are crafted at the Mobile Vehicle Bay, just like the Seatruck. Most of the ingredients shouldn't be new to you, except one. Plasteel Ingots introduces a new resource: Lithium. Combining it with Titanium Ingots creates an even stronger ingot. Lithium can be found in several biomes, but most easily they can be located in the Purple Vents biome from earlier. Once you've built the module, it'll drop into the water like the cabin. You can grab the handle on top of the module to drag it towards your Seatruck and attach it to the back. Make sure to attach the side with the handle to the back of the Seatruck.

Inside the Fabricator Module is a Fabricator. It can craft most of what a normal Fabricator can craft, except it can also craft Seatruck upgrades. By default, you get a few, any of which you can choose to craft, but the only one you need at the moment is the Seatruck Depth Upgrade MK1. This upgrade increases the Seatruck's crush depth to 300 meters. The recipe for it is quite simple (you can check it in the blueprints tab of your PDA). Once crafted, you can put the upgrade in the Seatruck by opening the hatch on the roof of the cabin. It is recommended that you keep your depth upgrade to fabricate the Seatruck Depth Upgrade MK2, and by extension, the Seatruck Depth Upgrade MK3.

Koppa Mining Site
The lady you saw was in a Prawn Suit; a vehicle that can walk along the seabed or above-water. It comes equipped with two modifiable arms and it very resilient to damage. Its blueprint can be found in two locations; the Glacial Basin and the Koppa Mining Site. The latter is slightly more dangerous, however it also contains an arm upgrade for the Prawn Suit, so you want to go there anyway. The entrance to the mining site is southwest of the Delta Island, about 120 meters down in the Thermal Spires; it is not far from the island. You'll know you found the entrance when you find doors in the wall of the biome. This entrance, however, is too small for the Seatruck to fit through, and it is nearly impossible to get all the way through the mining site on oxygen alone, no matter how much equipment you bring along (save for a network of Pipes; it may work, but it'd be expensive). Rather, you want to bring the Seatruck through the secondary entrance; it is found a short distance from the main entrance. It's in a crevice filled with volcanic geysers. It may seem dangerous to put a Seatruck through a small hole filled with lava geysers, but actually you can fit through pretty easily.

Once inside, you'll see a large hole in the ground with tracks going deeper, carrying large chunks of ore out of the cavern, though the site is no longer operational. Follow the tracks through the cavern to a platform holding a damaged Prawn Suit. This is a fragment you can scan; all four of the fragments are inside the cavern. By the first fragment is also a Prawn Suit Drill Arm fragment. You need two of these, and they are also inside the cave. A bit deeper within the cave you'll come across an area with the second drill arm fragment, which resembles some sort of loading dock for Prawn Suits. In this area there is a small console by one of the docks, next to which is a Prawn Suit Jump Jet Upgrade. You'll use it when you build your Prawn Suit. In this area is also a Data Box containing the Vehicle Upgrade Console, which is used to upgrade your vehicles. Make sure to pick it up before continuing, as well as scanning the two Prawn Suit fragments nearby.

A very short distance down the cave from the loading bay is a bend; the cavern splits into two parts. The left cave area contains a large artifact. They are not really needed to progress, but since you're in the area you should take the time to scan it. Artifacts can be found all over Sector Zero, and scanning enough of them will reward you with new hybrid technology.

The cave to the right is where the mining site ends. The elevator in the center of the room holds the blueprint for the Headlamp, a wearable Flashlight. Also in the room is the final Prawn Suit fragment. Collect it, and you should have everything you need from the mining site. You can exit from the same way you came in, or through a hole in the ceiling of the final room.

Prawn Suit
Now that you have unlocked the blueprint for the Prawn Suit and the Drill Arm, you can head back to your base or Drop Pod and craft them. The Prawn Suit is crafted in the Mobile Vehicle Bay, and requires 2 Plasteel Ingot, a Power Cell, 1 Enameled Glass, and 3 Lead, all of which you should know how to acquire. It can take a while to gather these resources, but it is rewarding. Once you build your Prawn Suit, it will sink to the bottom of the ocean, where you can enter it and start walking around on the ocean floor, with the same controls as you would use when walking on land. You can also control the left and right arms by clicking.

A Prawn Suit's arms is the core element of the vehicle. They can be modified to perform a large range of functions. In the mining site, you scanned the Prawn Suit Drill Arm, which can be used to mine large chunks of ore that you may have noticed in the mining site. To build the Drill Arm, you first need a Moonpool, which is attached to your base. Make sure to build the Moonpool somewhat close to the ground, so you can dock your Prawn Suit in it. Inside the Moonpool, you can build the Vehicle Upgrade Console (whose blueprint you picked up in the mining site) against one of the two smaller walls of the Moonpool. Once built, you can use the small fabricator on the wall by the console to craft the Drill Arm. The console also allows you to modify the name and color of any docked vehicles (you can also dock the Seatruck, and docked vehicles will recharge automatically). Make sure you have enough power in the base to run the upgrade console, as well as generate oxygen. See the Seabases page for power generation options. Both the upgrade console and the drill arm use familiar ingredients for their recipes. Once you have the drill arm, equip it onto your Prawn Suit with the upgrades panel on the side of the suit. It can also be accessed while undocked. Place the drill arm in one of the two middle slots, which represent your left and right arms. Then, you can use the drill arm by holding left or right mouse button. When looking at a large resource deposit, you will be able to drill resources directly into the Prawn Suit's inventory, which can be accessed from the back, on top of the suit just behind the hatch. Such deposits can be found in the mining site or later biomes.

Entering the Basin
When you head for the Glacial Basin, you will want to go through the Glacial Bay, as it is the infinitely safer route than the alternative Glacial Connection route which is packed with Jellyfish. This alternative entrance is deep down, under an ice front. You will have difficulties bringing your Seatruck through; fortunately, you do not need it in the Basin, so you can leave it there and navigate through the cave until you reach the surface. Once you surface, there should be a nearby dock you can use to climb onto the land. If you head through the Glacial Bay, you will receive a signal from a beacon outside of the Phi Robotics Center. Head towards it, and you can pick up the beacon to unlock its blueprint if you have not gotten it already. Immediately make your way up the nearby hill by climbing the stairs, which will lead to the basin wall where the Phi Robotics Center is located. Enter the cave to heat up, as the temperature in this area is very dangerous. While here, you may want to scan the Spy Pengling remains, as they will become useful later. Zeta Landon's bedroom contains a cold suit fragment, which will help the player withstand Sector Zero's freezing weather.

In the Glacial Basin, unless you have a Cold Suit equipped, the temperature is your greatest enemy. Due to the unusual climate of Sector Zero, blizzards are very common and they can quickly result in Robin's death. The Glacial Connection Lake, caves, and underwater tunnels serve as safepoints, where you can wait out a blizzard. Beware as well of Snow Stalkers, bear-like predators that will attack Robin on sight.

Snowfox
Your first goal in the basin should be to build the Snowfox. It is a ground-only vehicle that can quickly hover across the Glacial Basin. Its fragments are all over the area; you need three. In the Phi Robotics Center, you can also find the Snowfox Hoverpad, which is where the Snowfox is built. If you have not brought resources to build these, don't worry; all of the ingredients for the hoverpad and the Snowfox can be found in the basin. Titanium can be acquired from limestone outcrops, and batteries and lubricant can be found in supply crates. Build the hoverpad somewhere in the basin with the Habitat Builder and then build the Snowfox on it.

The Snowfox controls about the same as other vehicles; to move, mouse to turn. also causes the Snowfox to boost forward. The Snowfox can also be picked up and redeployed if you click on the back of it, behind the seat.

Frozen Leviathan
The end goal of exploring the Glacial Basin is to cure the Frozen Leviathan. It is located in the north-western corner of the basin, under a tall ice mountain. Before entering the cave, you can head south of the cave's entrance and pick up the Snowfox Hop Module blueprint from the tech site nearby. Afterwards, head into the cave. As you head into the cave, you may come across Parvan's Bunker. There are a couple of posters, a jukebox disk, and a few PDAs about the deceased security officer Parvan Ivanov. Further into the cave, the PDA will warn you that there is a leviathan nearby. When you get to the heart of the cave, you will see what the PDA means. If Al-An is within Robin's head upon entering the cave, he will indirectly inform Robin of its presence as well. A Frozen Leviathan is encased in a large cube of ice, and Alterra has been experimenting on it. Explore the cave; you can go up to the next level of the area using an elevator. This is where the head of the leviathan is. Synthetic Fibers, Fiber Mesh, and Silicone Rubber can be found atop a crate on the upper level. A lower tunnel in the ice carving leads to a chamber that was used to analyze the creature's claw. You can scan the claw. You can also pick up a vial of Hydrochloric Acid on a desk near the claw. At the end of the lower tunnel, you can scan a Prawn Suit fragment. The entrance to the main chamber of the cave is covered with debris, as a result of a cave collapse inadvertently caused by Sam Ayou setting off an explosive in an attempt to eliminate the Kharaa. An inactive crane is found on the opposite end of the chamber, next to a desk with Alexis Riedell's investigation report on the aforementioned incident. Before leaving the cave, you may want to pick up some Fevered Peppers; they are purple fruits hanging from small trees that warm Robin up when she eats them.

Hijacking Communications
After Marguerit Maida requests you to disable satellite surveillance, find and scan the Test Override Module fragment located on the table with Snowfox parts. There is also a Seatruck Perimeter Defense Upgrade near the table, it is advised that you pick it up. The blueprint for the Test Override Module consists of simple materials as well as a special item known as a Parallel Processing Unit.

To get the materials for the PPU ahead of time, find a Calaverite Outcrop in the Lilypads Crevice as you leave the area containing Marguerit Maida's base, and make sure you acquire at least one Gold. Head out of the Lilypads Crevice and head up the Lilypad Islands and knife one Table Coral sample and harvest one Silver Ore. If you already have these items on you or at your base, disregard this paragraph.

You will need to scan three fragments to unlock the PPU blueprint. There is at least one PPU fragment in each of the three Mercury II sections. It is expected at this point in the game that you have a Seatruck equipped with a MK1 Depth Upgrade to easily navigate to the entrances to any section of the Mercury II. It is advised that you bring an Ultra High Capacity Tank, and a Seaglide with the flashlight switched on with you when you enter either the stern or the bow of the Mercury II, as they can be difficult to navigate. Oxygen Plants can be found in both sections to buy you some time to locate the PPU fragments. Bringing a Laser Cutter is required for a couple of PPU fragments as some are sealed behind small laser-cuttable doors. Once you finish scanning all three PPU fragments, head back to Drop Pod (or your base if you have a Fabricator installed) and fabricate the PPU. The rest of the materials for the Test Override Module should be fairly easy to get. Proceed to fabricate the Test Override Modules once you have the materials.

Once you finish fabricating the Test Override Module, head to the Communication's Tower atop Delta Island and bring the module with you. Once you get to the tower, head up the ladder to the maintenance port, and insert the module. Then, head back down and select [Enter Test Mode] on the tower's terminal to complete the mission. You will receive a call from Marguerit Maida providing you vague directions to her greenhouse.

Repairing the Bridge
The Arctic Spires is inaccessible through normal means, as it requires that you refuel the bridge connecting it to the Glacial Bay. Find a ruptured Hydraulic Fluid fragment on the bay half of the bridge and scan it. The blueprint isn't resource-heavy and requires that you head to the Arctic Kelp Forest and to biomes containing gel sacks, provided that you don't have the materials. The nearest biome containing gel sacks is the Deep Twisty Bridges. Once you acquire the materials, fabricate one Hydraulic Fluid, and return to the bridge. Insert the fluid into the fuel compartment and you will gain access to the bridge's terminal.

Curing the Frozen Leviathan
After exploring around the Glacial Basin, you may have come across the Phi Excavation Site, an area housing the Frozen Leviathan. There is a sample injection robot located on the second level of ice carving, allowing you to eliminate the Kharaa Pustules dotted across the specimen. In order to do so, you must have a Spy Pengling as well as its remote, in your inventory. It is to be used to acquire the antidote that Sam Ayou stored away in a spy pengling site.

If you exit the cave containing the Frozen Leviathan, head south, past the Glacial Forest, and the frozen river bordering the forest's southern end. You should find yourself going up a hill and there should also be a light stick near the top of the hill. Head left, you should find yourself walking past the top of a frozen waterfall. Head down a slope leading down to the western end of the Glacial Connection lake. The Spy Pengling site containing the antidote should be just under the slope. Deploy your Spy Pengling and use it to collect the antidote at the end of the cave.

Return to the Phi Excavation Site, and insert the antidote into the sample injection robot. Interact with the terminal to commence the antidote injection into the Frozen Leviathan's Kharaa Pustules. After the injection succeeds, Robin will follow it up with a moment of closure regarding the death of her sister. On another note, if she has Al-An in her head, he will include some information on how Architects view closure.

Outpost Zero
You can access the abandoned base through a breach in the Sparse Arctic, northeast of the Drop Pod. You may want to bring a Seaglide with you, as the ice sheets above the Sparse Arctic prevent the player from replenishing oxygen. When you surface, you will be in a small cave with a few thermal lillies. From there, it is a straightforward path to the outpost, and beyond that lies the Architect Phase Gate Facility. In the base's laboratory, you can find an ion cube, a databox for the Control Room, several drawings done by Lillian Bench's children, a modification station fragment, a portrait of Potato (Robin and Sam's cat), and a few PDAs regarding Lillian Bench. The kitchen has several miscellaneous scannables, several posters, and a water filtration machine. You can scan the multipurpose room serving as the base's greenhouse and harvest the lantern fruit on the Lantern Trees grown in the interior growbeds. In the living quarters for Sam Ayou and Lillian Bench, you can find a portrait of Robin holding Potato, more miscellaneous scannables, and more of Lillian's kids drawings as well as a poster of the Quarantine Enforcement Platform from the crater.

Omega Lab
The location of Omega Lab is hinted by Marguerit Maida shortly after she finishes talking to Robin at her greenhouse. To access the lab, which is found at a depth of 200 meters inside the largest suspended landmass in the Lilypad Islands, it is advised that you drive a Seatruck equipped with a Seatruck Depth Upgrade MK1. You will find the base in disrepair, as a result of Marguerit torching the base, which subsequently caused the base's nuclear reactor to detonate. You can find a few PDAs in the base revealing that the Omega Lab was the research center for experimenting with Kharaa from the Frozen Leviathan. You will also discover that the base quartered the researchers Vinh Pham and Danielle Valenti. In the outpost's large room you can scan the nuclear reactor, a power cell charger, and a couple of command chairs. An exclusive miscellaneous buildable, the Aromatherapy Lamp, can be found in either multipurpose room. Both multipurpose room glass domes are scannable as well.

Encountering Marguerit
As Robin traverses up the Delta Island, she will briefly encounter Marguerit in her modified Prawn Suit, threatening her to stay off her land. Shortly before she leaves the island, she will tell you not to follow her. However, this is an incentive for you to follow Marguerit. Robin will then remark on how she was not as alone as she anticipated. It should be noted that this cutscene will allow you to access her seabase.

Marguerit's Seabase
To get to Marguerit Maida's Base which is located 380 meters underwater, it is advised that you have a Seatruck equipped with a Seatruck Depth Upgrade MK2, which can be crafted in the Vehicle Upgrade Console or a Seatruck Fabricator Module attached to a powered Seatruck. The base is accessible from the western corner of Lilypads Crevice, indicated by clusters of Hivemind plants. It is also accessible from the fissure under the northern Ventgarden in the Tree Spires. When Robin enters the base's large room for the first time, Marguerit will request her to disable the Communications Tower on the Delta Island shortly before she walks into the adjacent large room. The rest of the rooms contain special interior modules including the Fridge, Sink, Toilet, and Shower. All but the fridge serve no practical purpose. Her Snow Stalker will obstruct Robin from entering the other rooms of her base, until Robin hijacks the Communications Tower. For the time being, you will scan the Test Override Module and pick up the Seatruck Perimeter Defense Upgrade lying on the rug the workroom table sits upon. You can pick up Marguerit's third log in the workroom, and the fourth log in her bedroom. Her seabase is locked by default until you encounter Marguerit on the Delta Island.

Marguerit's Greenhouse
After Robin disables the Communications Tower, she will receive a call from Marguerit providing her vague directions to her greenhouse. Marguerit's greenhouse is located on the south-eastern iceberg in the East Arctic. The shoreline of this iceberg is marked by a few crates, light sticks, and part of a skeleton. Just before the bulkhead, you can find a PDA of Marguerit describing the difficulties of gardening in Sector Zero. Robin will receive a hint towards the location of the sabotaged Omega Lab after conversing with Marguerit in her greenhouse. You can also harvest a variety of edible flora, as well as unlock the Spicy fruit salad, which will replenish a great deal of your body temperature, hunger, and H₂O, by scanning any of the Snow Stalker fruit plants inside the greenhouse. It is recommended to use Spicy fruit salad as your main food source from now on as it gives the most food and good H₂O, does not rot, and only takes 1 slot in your inventory. A free bottle of Disinfected Water and a Nutrient Block lay on a nearby shelf.

Al-An's Storage Medium
Al-An requires a new storage medium so that he may perform a wider range of functions than Robin's brain allows. In order to do that, Robin needs to collect certain parts, which are located in various Architect Caches around Sector Zero. It should be noted that until Robin downloads Al-An into her head, the caches will remain inaccessible.

Preparation
The first cache is located in the Arctic Spires, an aboveground biome connected to the Glacial Bay. The Cold Suit you picked up earlier is very useful in the spires, however it requires a resource you don't yet have; Snow Stalker Fur. Hopefully, you scanned the Spy Pengling fragments in the while in the basin. If not, go back and scan it. The pengling is simple enough to build and doesn't require anything you haven't seen yet. You also need to build a Spy Pengling Remote to operate the pengling. Once you have built both, head back to the Glacial Basin and place down the Spy Pengling, then equip the remote and right click to activate it.

Spy Pengling controls are different than most vehicles, though simple enough. to move forward and backward, and to turn left and right. Left click to pick up with the pengling. Press to exit the pengling. Take care not to drive the Pengling into water or more than 50 meters away from Robin. To acquire Snow Stalker Fur, you must find a Snow Stalker and grab at it. You need 4 furs, but you can get all of them from a single Snow Stalker with ease. To take the furs from the Spy Pengling, simply go to it and open its storage with left click. Then head back to a fabricator and craft the Cold Suit (you also need some Fiber Mesh). Make sure to craft all three pieces, head, body and gloves for the full protection. The suit greatly helps to combat the effects of the cold.

It is also advised to increase the mobility of your Snowfox by crafting a Snowfox Hop Module in the Vehicle Upgrade Console, assuming you picked up the blueprint from the basin, near the Glacial Basin forest. Add it to your Snowfox by opening the upgrades panel on the left side. Once you are ready to head into the Arctic Spires, head back to the Glacial Bay. If you have not yet repaired the bridge, do so.

Through the Canyon
The entrance to the Arctic Spires is located on the northern end of the Glacial Bay, on a high-up plateau connecting to the spires with a bridge. You will want to ride your Snowfox into the spires. Not too far into the canyon, you'll find a tech site with a large crane; this site contains the Thumper blueprint. It is in your best interest to go back home and craft multiple Thumpers.

If you did not meet one on the way to or from the tech site, then you have yet to encounter what is known as an Ice Worm. The Ice Worms are land-based leviathans that burrow through the ground, listening for prey to ambush from below. Their aggressiveness and stealth make the Arctic Spires possibly the most dangerous biome in the Subnautica series. Even the sound of Robin running or the Snowfox moving will alert them to Robin's position, where they can very quickly and quietly kill Robin in few blows. In order to get through the canyon, you may need to employ the use of Thumpers, which create sound when placed and lure Ice Worms towards it while Robin makes a getaway.

Ice Worms are very versatile predators. They can dive out of the snow towards you, pop out of the snow under you, or burrow through the ground and make a short jump. They can attack from inside caves or even from the walls. Even the small tunnels located under the Arctic Spires are their hunting grounds; though not very damaging, their poke attacks are repetitive and can kill you. To get through the area, a combination of Thumpers and a large amount of First Aid Kits is recommended.

Arctic Spires Cache
The Arctic Spires Cache is nestled in the deepest region within the Arctic Spires, within a depression in the rocks.

The Arctic Spires Cache is home to one Ion Cube, one Ion Cube Deposit, and the tissues for Al-An's Vessel. The Ion Cube Deposit is not as in the previous game fabricated at a factory, so this can be harvested once only. Once the tissue has been scanned, you will get a blueprint Architect Tissues, allowing you to collect materials in preparation for the vessel.

Preparation
The second cache is located in the Deep Lilypads Cave. Before going to the Deep Lilypads Cave Cache, you should ensure that you have food and water to survive one to two in-game days. This cache is 620 meters deep, so by now, you should have the Seatruck Depth Upgrade MK3. Make sure you also have enough room in your inventory to pick up a few items. The cave houses a material that is needed in order to craft Al-An's Vessel which is the Deep Lily Pad Mushroom. You will need to pick up 3 Deep Lily Pad Mushrooms as you will need to craft 1 Hydrochloric Acid. You will also need to pick up a Flower Spore to unlock the Hydrochloric Acid blueprint, though the spore is not required to create it.

Deep Lilypad Islands Cave
This cave is located just below the large suspended island where the Omega Lab is. This floating landmass can be found if you travel south of the Purple Vents, or east of the Tree Spires. The Squidsharks along the way should not pose a threat at this point.

Once you reach the suspended island go down the crevice around it until you reach the bottom. Once reached, find the one of the two tunnel openings leading further down, and follow the alien structures until you reach the Deep Lilypads Cave Cache. Be sure not to go all the way inside your Seatruck, as it is possible to get it stuck inside the cache. Inside you will find the Skeleton Component needed for Al-An's Vessel, scanning this unlocks the Architect Skeleton.

Preparation
The third cache is hidden in the Crystal Caves. As this is the last part in the process of creating Al-An's Vessel it is recommended that you bring along the items to craft all 3 parts. In total you will need: The Crystal Caves are home to several Shadow Leviathans, so make sure your gear is charged, or bring along spare Batteries and Power Cells. If you decide to bring you Seatruck with a few modules, it's a good idea to have the Horsepower Upgrade and/or the Afterburner Upgrade installed, as these will help you pass the danger quicker. These upgrades can be found in Sea Monkey Nests near the crashed ship. You can also choose to install the Perimeter Defense Upgrade, as this can shock predators, hopefully prevent Shadow Leviathan attacks.
 * 4 Titanium
 * 3 Kyanite
 * 3 Magnetite
 * 3 Nickel Ore
 * 2 Lithium
 * 1 Aerogel
 * 1 Ion Cube
 * 1 Polyaniline
 * 1 Synthetic Fibers

By this point you absolutely need the Seatruck Depth Upgrade MK3, since the last destination is just below 900 meters.

Get to the Crystal Caves
There are a few entrances to the Crystal Caves, the safest and easiest is located in the Lilypad Islands biome and is fairly close to the large suspended island above the Deep Lilypads Cave. The entrance is connected to a small system of tunnels, which is also home to several Sea Monkey Nests. Located a site where 2 Squidsharks roam, and what looks like Precursor Technology. This area leads down to Marguerit Maida's Base. Her base has a Moonpool and a Large Room Glass Dome, which can be scanned for base building. If you have not been here yet, she will call you inside for a quick chat, you can go in through the Moonpool. When the chat is over you can pick up a Seatruck Perimeter Defense Upgrade behind you, and explore her base to scan a Toilet, Shower and Sink, which also can be use to decorate your own base. After this you can leave her base, and proceed deeper towards the Crystal Caves.

In the entrance to the Crystal Caves from Marguerit Maida's Base, several Prawn Suit Propulsion Cannon fragments can be found across the bottom.

Crystal Caves Cache
Once inside you can encounter the Shadow Leviathan, try to find an opening where the Leviathan circle the opposite site of the cave to avoid getting attacked. The Shadow Leviathans will circle around two crystal formation that leads down to the Crystal Caves Cache, where the Architect Organs can be found and scanned. There are two entrances, the Northern Crystal Castle Entrance, and the Southern Crystal Castle Entrance. It is hard to avoid getting attacked if you park your Seatruck down inside the crystal formation, however it is possible to fit down the hole if you only have a few modules attached. Your Seatruck can handle a few hits without getting destroyed and the Shadow Leviathans will ignore you for a bit after an attack.

You will have to leave your Seatruck behind for a bit while following a narrow path leading down to the cache. Once inside follow the road, and you will eventually reach the Architect Organs which unlocks the last piece of Al-An's Vessel after scanning.

Creating Al-An's Vessel
To craft Al-An's Vessel you need access the Fabricator Base found in the deepest part of Fabricator Caverns. It is located deeper inside the Crystal Caves and can be spotted by its characteristic red colored crystals. There are two tunnels leading down, each with its own Shadow Leviathan. Follow either one and try to find a space to park your Seatruck as you will have to leave it. The entrance to Fabricator Base is just below 900 meters, so you will have to swim or drive a Prawn Suit the rest of the way.

Inside the base on the left side is 3 terminals. Each terminal is responsible for crafting one part of Al-An's Vessel. Input the materials into each terminal and start the fabrication process of the vessel.

After crafting the vessel, Al-An will tell you to meet him at the Architect Phase Gate Facility, which is near Outpost Zero.

(The end of the story has not finished yet.)