The Malfera is a creature from the Nightmare Dimension that is only encountered on the Prime as the result of a powerful summoner.

It first appeared in module X-5, pg. 28.
Companion Rules Set, pg. 34
Rules Cyclopedia, pg. 191
Savage Coast Monstrous Compendium, available on the Vaults of Pandius
Creature Catalog V, Sean K. Reynolds, Dragon 343, pg.51 ?

pictures: From SCMC & From Steve Ellis in Dragon

Monstrous DB for OD&D

2e stats from the SCMC

3e stats by Travis Laney 2007

3e stats by Valentius July 2005

See its Monster Lore entry by Gary Davies June 2007

4e stats by John Walter Biles Jan. 2009