Gaunt horses of the lower planes with glowing eyes and burning hooves

Nightmares, also known as Hell Steeds, are the horses of the lower planes. Nightmares are gaunt beasts with eyes that glow fiercely red and orange, fire and smoke blowing from their nostrils, and hooves that burn like fiery coals. Nightmares are able to change sizes, from the size of a warhorse up to a giant form twice that size, but despite these changes their statistics (hit dice, attacks, and so on) are not affected. This ability allows them to serve as steeds for demons and devils of various sizes. Night hags (page 154) and sometimes greater undead such as vampires, spectres, and liches may use nightmares as steeds.

Otherworldly black warhorse with blood red eyes, fiery nostrils, and burning hooves that serves as a mount for powerful evil beings

Nightmares serve as mounts for powerful evil beings. Whilst in shape they resemble large warhorses, they are unmistakably otherworldly, having blood red eyes, fiery nostrils, powerful fangs, a midnight black coat, a mane of shadow and hooves that appear to leap aflame when they run. Though it is known that Nightmares can understand what their riders ask of them, they are not thought to be able to speak themselves; but they seem to be able to communicate with one another well enough. Although most Nightmares do not possess wings, they can fly through the air considerably faster than they can run along the ground. Their capacity for such swift flight is greatly valued by those they serve, as is their ferocity in combat. Nightmares hate living creatures and, being given to viciousness, will generally attack any non-evil entity they encounter. They use their fangs to bite for 2d4 damage and strike with their hooves 1d6+4 damage, which will also set any flammable objects they strike alight. In their excitement, Nightmares are also known to produce a noxious smoke that causes anyone within ten feet to have to save vs paralysis or suffer a -2 penalty "to hit" and damage whilst in the vic