Going for a high powered baddie this week. Amdusias is one of the Dukes of Hell. Not sure if he's already statted up for AD&D somewhere, but here's a non-unique version of the devil that could be a follower of the duke, if you prefer.
AC: -2 (22)
Move: 120 (40)
Attacks: 1 gore or spell
No. Appearing: 1-4 (1-4)
Save As: Fighter 15
Treasure Type: H
Amdusians are large storm devils with human-like bodies and black unicorn heads. They stand 12' tall. Their purpose is to spread cacophany and discord, although they can create beautiful, if disturbingly haunting, music when they choose. Amdusians can be summoned to the Prime Plane by a Magic-User who knows the proper ritual, but they can be difficult servitors unless the mission they are given is not adequately destructive.
Amdusians are immune to normal weapons. In combat, they may gore with their horns, or use spells. All Amdusians can use a lightning bolt, as the spell, for 10d6 damage up to three times per day. Once per turn, they can create a thundering blast of sound (treat as a Horn of Blasting). Amdusians are immune to all electrical and sonic damage and effects, and to Silence 15' Radius spells.