The recruitable demons/creatures/deities/historical figures as they are depicted in the Megami Tensei franchise. They are featured in the mainline series (Shin Megami Tensei), and spin-off series/games (Persona, Devil Summoner (Series), etc.)
See: List Of Shin Megami Tensei Demons for a list of them ordered by the race they typically appear as in the mainline Shin Megami Tensei games.