Astisanax

These fish can only be found in specific caves around the world. These caves seem to have natural formed lakes. It is believed that during a flood a long time ago the fish were swept into the cave by the current and got stuck in those lakes and thus never made it out. Every cave that has these fish has their own subspecies, evolved to the specific conditions of that cave. What they all have in common is that every subspecies has lost their eyes, as those are not needed anymore in the depts of the caves.
It is said that the skull of any of the subspecies can be used to make a Poison of Blindness (recipe).   They also exist in the Depths but are much more rare. They are not magivores but are so metabolically efficient that they can survive by feeding off the debrids of other fauna.