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.