Unique to all the faerie races is the Faey; also known as “Dark Elves” (their skin loses its colors and turns dark), Fey (most common), Fay, Fae, and Faye. Fae is an ancient root of Faerie, and along with the right accent means those-who-claim-nourishment-alone. The Fae are those which have, through some means, turned into a creature who revels in evil, maliciousness, and causing chaos. Unlike most aberrant behavior, it is not a mental illness of organic origins. Instead it is something which is ‘chosen’. To become a vessel of death, discord, and hate is not something a rational creature simply chooses without serious trauma, disorder, or social conditioning. All Fae are elven in nature, and a corrupted ancient Aelf is the worst of them all. Other faerie subspecies make unsuitable vessels for such dark power, wilting and dying early in the process. Fae that survive often seek out the outcastes (example: Faet m’un of the Steel Realms) if any exist in the world on which they dwell, and become part of their society.
Once the creature has undergone their full transformation, if they survive, they may choose self imposed exile from the mortal worlds and exchange for an endless hunt, preying upon Aelfpath travelers, and those seeking the Feywild. Typically, such creatures are more powerful than mere humans of the mortal realms, and so this choice (which cannot be undone) is about the savoring of the more powerful souls they will consume.
The character is transformed into a Fae/Drow. They lose all their previous racial features and gain all those associated with Drow. Generic Fae are not bound to serving a specific fiend, but are bound to their evil. Trying to return to their previous state will kill them, no save.