Nightmare (creature)

A nightmare is a neutral evil outsider from the Lower Planes that resembles a large black horse with flames wreathing its hooves and trailing from its nostrils and red eyes. A nightmare will sometimes serve powerful evil creature as a mount. While possessing the ability to travel to other planes, a nightmare can bring its rider therewith.

Obsidian Steed
Nightmares can also be summoned using the obsidian figurine depicting an almost skeletal horse with wide, flaring nostrils. Upon uttering the trigger word "Blackfire", the magical item erupts in black and purple flames, bringing forth a nightmare for a period of time in which the wielder has control over the creature for the duration of its indenture. After which the creature returns to its home plane to rest until you can call it again. The figurine's weight then seems lighter but increases as its magic begins to gather anew.