BOZ said:here's one. this isn't exactly canon, but in White Dwarf mag, there were once Horsemen of Orcus.
Arendagrost, Maw of the Abyss. According to accounts at the time, the beast vaguely resembled an immense wingless dragon of gargantuan size. Instead of legs, it moved upon a sea of tentacles. In place of scales, it was covered in coarse black fur and had three heads that resembled monstrous horned fiends that breathed bloody acid, fire, and frost. Its six-fold eyes offerend instant death to anyone catching their hideous gaze...