Dungeons & Dragons Players' & DM's Guide to Immortals TSR 1986
Immortals Rules, Dungeon and Dragons Fantasy Role-Playing Game Set.
Players' Guide to Immortals - Featuring rules for creating new characters and their form, abilities, powers, and home plane. Also includes rules for creating new artifacts.
Dungeon Master's Guide to Immortals - Introduction rules for Immortal level characters. Plus Immortal and other-planar creatures.