Type VI Demon (Balor, etc.)
I drew this image to supplement an AD&D adventure that I was creating. The being is from Monster Manual I, Gary Gygax: "With proper invoking, offerings, and promises Type VI demons might be convinced to co-operate with a character or group for a time. Naturally the demon will attempt to assume/usurp command at every opportunity. Most chaotic evil monsters are drawn to the strong evil charisma of this creature, and of all its kind, the type VI demon tends towards a more organized evil (which makes it less than popular with demon lords and princes)."
This one is pictured mounted on an unnamed abyssian beast, more for symbolic reasons than for any need of a steed.