Fell Nightmare

Evil. The nightmare radiates an Evil aura.

Fiery Hooves. The nightmare sheds bright light in a 10-foot radius and dim light for an additional 10 feet. The nightmare leaves charred hoofprints.

Fire Resistance. The nightmare can grant fire resistance to a rider.

Fiery Trail. When the nightmare moves along the ground, it can choose to leave behind a trail of fire 10 feet wide and 10 feet tall, which lasts until the beginning of the nightmares next turn. A creature that begins its turn in the fire or enters it for the first time on a turn takes 10 (3d6) fire damage. The trail ignites flammable objects.

Telepathy. The nightmare gains telepathy with a range of 120 feet. It can telepathically communicate with the fiend that trained it over any distance as long as they are on the same plane of existence.

Hooves. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage plus 7 (2d6) fire damage. If the horse moves at least 20 feet straight towards the target before the attack the target makes a DC 14 Strength saving throw falling prone on a failure. The nightmare can move through the space of a prone creature as long as it does not end its turn there.

Ethereal Shift (Recharge 5-6). The nightmare and a rider magically pass from the Ethereal Plane to the Material Plane or vice versa.