Hadean biosphere

I suggest creating a deep biome. There would be life living on the sea floor which would be so deep, no light would reach it. Since Proteus doesn’t have any photoproducers anyway, it wouldn’t be so far fetched. Instead there could be chemo-synthetic or radiation-synthetic organisms as a base of a complex foodchain. The foodchain and deep sea gigantism could sustain large blind leviathans with echolocation.

There’s implications that Proteus did have thriving plant life at one point which has since gone extinct either due to the heavy metal saturation in the water or the proteavirus just mutating the plants out of their ecological niche