Reaper Leviathan

The Reaper Leviathan is a large, hostile creature that does not yet spawn naturally.

The Leviathan's model can be seen here.

Early animations for the Reaper Leviathan are available on Trello.

The Reaper seems to move around its prey for a few seconds before attacking. In the future, it will spawn around and defend the crashed ship. Currently the Reaper doesn't harm the cyclops, though it has enough strength to push it.

It can currently be spawned in experimental mode using the command SPAWN REAPERLEVIATHAN and another, smaller, brown leviathan can be spawned using SPAWN LEVIATHAN though it does not appear to move. The creature resembles this creature very closely, which appears to be called the Sea Emperor.

If fins and head protrusions are included, the Reaper Leviathan currently is about 2.5 times as high and about 2 times as long as the Cyclops.