The Court of Nevernight

Contrary to what outsiders believed, the deepest level of the labyrinth of the Dark Abyss wasn't shrouded in complete darkness. While the upper levels sure do pose a threat to anyone who dared to enter the labyrinth, no one was able to reach the lowest level so far.

This was the great labyrinth that Arman, the Black Mage, had created during his reign. Many darklings and magi came to the Dark Abyss to seek power, but most of them were devoured by their own darkness and eventually lost their sense of identity.

This made them part of the monsters that reside in the labyrinth and become part of the levels they were able to reach. The deeper one managed to enter, the more grotesque and powerful the monsters were. However, if one managed to reach the deepest level, they might surmise that they entered an illusion instead.