The nabassu (major demon) first appeared in the first edition Monster Manual II (1983).
The nabassu (greater tanar'ri) appeared in second edition in the Monstrous Compendium Volume Outer Planes Appendix (1991). The nabassu (greater tanar'ri) also appeared in the first Planescape Monstrous Compendium Appendix (1994).
Nabassus are demons very close to undead creatures. Nabassus resemble dark horned demons with bat wings, evil glowing eyes, sharp teeth and long talons. The life of a nabassu is composed of two stages: during the first one, the juvenile nabassus reside on the Material Plane, looking for victims in order to feed on and evolve; during the second one, the mature nabassus come back to The Abyss where they usually live in an Abyssal fortress or become a servant of Orcus.