Alps are a succubus-type monster girl with a very unusual origin: monsterized homosexual men and those who yearned to become women. If such men become incubi from exposure to demonic energy, the dark magics respond to their desires by turning them female. Although alps may begin their monster lives looking rather androgynous, by feeding on enough spirit energy their transformation can turn them more feminine and lascivious than even a regular succubus.
Monster Girl Encyclopedia
