Shadow Leviathan

The Shadow Leviathan is a species of Leviathan-class predator found in the Crystal Caves and the Fabricator Caverns. It is the second-largest aggressive aquatic creature, and fifth largest overall.

A total of four Shadow Leviathans can be found in Sector Zero, two in the Fabricator Caverns and two in the Crystal Caves.

Appearance
The Shadow Leviathan has an elongated black body with smooth skin and twin rows of 37 small red spots running from behind the head to just before the tip of the tail. Below each row of red spots is a shorter row of eight circular gill pores that run down the side. The head is composed of a triangular shield-like structure with three pairs of small black eyes and a large red ring in the center. The creature possesses a flexible spinal cord allowing it to contract and retract its head. The creature's mouth is located on its underside just behind the head: it is a glowing blue tone, and lined with curved teeth resembling a ribcage with the sternum removed. The mouth appears to pass food directly into the creature's stomach, with no real throat structure present.

Seven pairs of jointed clawed appendages run down the sides of the mouth. These have spines along the inside edge to assist in securing prey. Seven more pairs of these appendages can be seen running down the body, decreasing in size as they get closer to the tail to the point that the final three pairs are little more than a small spine. This gives the impression that these grasping appendages once served as walking limbs in a distant bottom-dwelling ancestor, but have since been repurposed into their current form.

Propulsion comes from the large fins on the rear portion of the Shadow Leviathan's body. Though lacking a tail fluke, a large fin is present around halfway down the body on both the dorsal and ventral sides, the ventral fin having smaller fins in front of and behind it. The tail ends with a red point.

Design
The tail portion of the body is very similar in appearance to the black ghost knifefish and the row of holes on the body resemble the gill openings possessed by lampreys. The mouth and mandible design was based on the heads of arrow worms. It also bears a striking overall resemblance to aegirocassis, with its oblong proboscis, hanging feeding appendages, and many bilateral limbs.

A scrapped alternate design closely resembled an oversized, predatory Sea Monkey.

Behavior
The Shadow Leviathan will grab the player’s Seatruck or Prawn Suit to attack, pulling the vehicle into its mouth dealing damage until it is released. When the seatruck is in its mouth, the Shadow Leviathan will spray a blue liquid from its mouth, which is confirmed in the databank to be acid. If the Shadow Leviathan attacks the player under 75 health, a cinematic death scene will instead play.

Bizarrely, although Shadow Leviathans do not attack small prey fish such as the Red Feather Fish, they will attack most hostile fauna. This includes the Brute Shark and the Chelicerate, it is unknown if they are prey to this colossal creature. Due to the Shadow Leviathan commonly not targeting smaller Fauna, it is recommended to proceed with caution when entering its territory, as the Shadow Leviathan will likely attack the player immediately on sight.

If the player is being pursued, it is recommended they take cover in a fissure or among the biome's Large Morganite Formations where the Shadow Leviathan cannot reach them. It will usually give up after a short time, though it may take a while to return to its usual patrol path afterward. It is also possible to kill a Shadow Leviathan however it requires careful movement and the correct arms on your Prawn Suit, usually Drill and Grapple Arms. Shadow Leviathans do not respawn upon being killed.

Gallery
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Trivia

 * The Shadow Leviathan has the most known concept artwork of any fauna species in Subnautica, with 21 pieces having been released and several more versions that have not been released.
 * The Shadow Leviathan seems to be a relative of the Ice Worm.