A Nightmare is a malevolent magical beast that appears in the Dungeons & Dragons roleplay game. Named after the horrifying dreams suffered by mortals, these outsiders resemble ebony-black horses with manes and tails of pure hellfire. Residing in the negative plane known as the Shadowfell, Nightmares are cruel and sinister creatures that delight in striking fear into their prey before moving in to devour them. Though intelligent creatures in their own right, they often submit themselves to evil beings of even greater power, serving as mounts for fiendish warlords. Such villains can only gain the service of a Nightmare by defeating it in battle first, the only alternative for the Nightmare being death if it does not submit after defeat. When a Nightmare dies, its flaming mane and tail will extinguish and be reduced to ashes.
- Hell's Ride - Being partially comprised of fire, Nightmares have a high resistance to fire-based attacks, a protection they also grant their riders.
- Hooves of Hell - When a Nightmare's prey tries to escape, a Nightmare will usually teleport in front of them to cut them off, then trample and burn them with its flaming hooves.