Apple is a human, one of the Ever-Dying. Influential in Notte’s life, she was one of Horse’s rescues, and she helped teach Notte during his time in the city of Az’Kabek.
Also, incidentally, Apple is based off a wonderful reader: AppleBison.
Also incidentally, her natural pigmentation tends toward pink. Don’t blame me. The character demanded it. (And please don’t kill me, Kelli!)