This eerie horse-like creature’s skin is an inky blackness. Fire spurts from its hair and nostrils, and its hooves spray sparks.
Speed 40 ft., fly 90 ft. (good)
1/day (self plus 1 rider only)—plane shift
Str 18, Dex 15, Con 16, Int 13, Wis 13, Cha 12
In battle, a nightmare exhales smoke that chokes and blinds foes, filling a 15-foot cone each round as a free action. Anyone in the cone must succeed on a DC 16 Fortitude save or become sickened until 1d6 minutes after leaving the area. This smoke acts as obscuring mist for the purposes of concealment. The smoke persists for 1 round. The save DC is Constitution-based.
Source: Chris Malidore
Nightmares are flaming harbingers of death. They allow only the most evil of creatures to ride them, and are never mere mounts, but rather willing partners in destruction.