Feasibility of the rotten vale

Question

I recently asked a question about’ “The feasibility of the coral highlands”, which come from a game called “Monster Hunter World”. In the game, there is another place, called, “The Rotten Vale”, which is essentially a sea of dead body’s.

The Rotten Vale resides right under the coral highlands, and is littered with dead body’s, rotting corpses, toxic fumes, and much much more. Like I said, the rotten vale is covered in a toxic layer of fumes which are actually a type of bacteria that can lower your health, or in this instance, kill you slowly, and is capable of turning even the most passive of creatures into aggressive beasts.

Deeper into the Vale, there resides pools of glowing acid, aside from this fact, I’m going to describe some of the life that live down there to hopefully give a better grasp of the question

So the plant life that resides in the vale consists of molds, mushrooms, funguses, pitcher plants, and sundews.

The animal life seems to be in a extremely slow state of flesh decay, however, a few apex predators seem to have adapted to this life with one adapting to losing its fur and replacing it with scales, another seemingly having a symbiotic relationship, in which allows for this creature to control the bacteria.

In the game The bacteria is known as the effluvium, which in and of itself is most likely a flesh eating bacteria.

So now that I’m finished with the descriptions, I’ll tell you what such place got me thinking about:

1. Is it feasible for the rotten vale to exist

2. How would a real world creature evolve to such nigh-inhospitable conditions

Answer 1

Places like this exist in the real world. They are called endoheric basins - essentially, water flows into them, but doesn't flow out. They are most commonly found in hot, dry regions, where the rivers that flow into them are offset by evaporation, keeping them at a more or less constant size. A constant inflow of salt and other minerals creates a highly saline and often toxic environment that few animals can live in.

Relatively new endoheric lakes, such as the Salton Sea (which was created accidentally by a botched canal construction project), are particularly vile. Fish still live upstream, so as the rivers drain into the basin they wind up filled with fish that die in the lake and rot. This breeds algal blooms and various assortments of putrefactive bacteria, as well as attracting birds and other animals that try to feed on the dead fish - and are likely to catch diseases from the conditions, adding their own bodies to the pile. Needless to say, it is disgusting.

Conditions such as these don't last forever, though. Endoheric lakes are prone to drying out, and there's only so many fish you can feed into a lake before whatever upstream source they are coming from starts to run out. Some old endoheric lakes, such as Lake Urmia, are home to salt-tolerant mollusks and the birds and reptiles that feed on them, while others, like the Dead Sea, support nothing but a few extremophilic archaeabacteria and tourists.

But a Salton Sea situation can last for several decades at least, so as long as you don't need the Rotten Vale to stay that way forever, that's a fairly decent explanation for its existence.