[...] They often offer human sacrifices to the absolute monster, because they believe that the Great Old One would not be able to move on its own, needing to ingest human bodies to absorb their vital energies, thus keeping it's cosmic body awake for as many aeons as possible.
~ Sergio Sbeghi about Bärkatlànm

Bärkatlànm is a Great Old One. But different from many other Great Old Ones, he doesn't seek the destruction of mankind; he needs mankind's faith to be able to move his body. Also unlike some other Great Old Ones, he is not sleeping, but is active. Bärkatlànm walks the Earth in the guise of an animal.

Many call him the Owner Of All Thoughts, as he may command anyone's mind - but he doesn't do so often. As a servant of his summoner, Azathoth, Bärkatlànm is the Watcher of human minds - "The Abyss" as he calls it so - and he wills to spread madness.

Bärkatlànm, also called the Scaleless Fish, is stuck in his serpent-fish-like body. This one is invulnerable, but he is theoretically mortal. Supposedly, it is possible to kill Bärkatlànm by assassinating his current Avatar.