Baalzebul

Baalzebul is the "archdevil of the sixth and seventh planes of Hell" who features in the adventure Death Trap by John Nelson. Described simply as a "devilish looking being", he appears in a limestone room within the Death Trap mountain caverns and is extremely resilient and dangerous, having a hardiness of 366 and inflicting 3d12 barehand damage. If defeated he vanishes in a puff of foul smoke and returns to his place in Hell.