Cauchemar

Aura of Dread. A creature hostile to the cauchemar that starts its turn within 20 feet of the cauchemar must succeed on a DC 14 Wisdom saving throw, unless the cauchemar is incapacitated. On a failed save, the target is frighteneduntil the start of its next turn. While frightened in this way, the target can't perform any actions except move up to half its speed. If a creature's saving throw is successful, the creature is immune to the cauchemar's Aura of Dread for the next 24 hours.

Confer Fire Resistance. The nightmare can grant resistance to fire damage to anyone riding it.

Illumination. The nightmare sheds bright light in a 10-foot radius and dim light for an additional 10 feet.

Multiattack. The cauchemar makes two attacks: one with its bite and one with its hooves.

Bite. Melee Weapon Attack: +9 to hit, reach 15 ft., one target. Hit: 13 (2d6 + 6) piercing damage plus 10 (3d6) fire damage.

Hooves. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 20 (4d6 + 6) bludgeoning damage plus 10 (3d6) fire damage.

Ethereal Stride. The cauchemar and up to three willing creatures within 5 feet of it magically enter the Ethereal Plane from the Material Plane, or vice versa.

Sulfur Breath (Recharge 5-6). The cauchemar exhales nauseating sulfurous smoke in a 15-foot cone. The smoke spreads around corners, and its area is heavily obscured. Each creature in that area must succeed on a DC 16 Constitution saving throw. On a failed save, the creature takes 14 (4d6) fire damage and spends its action on each of its turns retching and reeling for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. Creatures that don't need to breathe or are immune to fire automatically succeed on this saving throw. On a successful save, the creature takes half as much damage and does not suffer any other effects.