Leviathan

Leviathan was an Agathinon who surrendered its estate as Aenir to live upon Erenth. Greatly diminished in strength, it has become an agent of chaos, acting as a wild and raging beast. It has been banished beyond the Outer Sea to the Sea of Certain Death. 

A Definition of the Sea and Index of the 11 Seas

In the largest sense, The Sea is the interconnected salt waterway that surrounds all of the landmasses of Erenth. In a local sense it is divided into specific, smaller bodies of the seas and each of them is given a specific name such as the Dagger Sea. Despite this naming convention, there are no rigid distinctions between the end of one body of water and the beginning of another.

Note that the Sea of Glass and the Sea of Grass, are not seas at all.

• Dagger Sea a/k/a Sudmen's Sea(n) Narrow Sea(e)
• Great Sea a/k/a Wide Sea(n), Inner Sea(s), Golden Sea(e)
• Outer Sea a/k/a Crimson Sea(e)
• Sea of Certain Death(w)
• Sea of Despair(e) a/k/a Krakentoan Sea(e)
• Sea of Limitless Fury(s)
• Sea of Ice a/k/a Draugr Sea(n), Mumin Sea(e)
• Sea of Tumult(s)
• White Sea(s)
• Tranquil Sea(a)
• Sea of Shards