Large Fiend, Neutral Evil
Armor Class 13 Initiative +2 (12) Hit Points 68 (8d10 + 24) Speed 60 ft., Fly 90 ft. (hover)
Saving Throws Str +4, Dex +2, Con +3, Int +0, Wis +1, Cha +2
Damage Immunities Fire
Senses Passive Perception 11
Languages Understands Abyssal, Common, and Infernal but can't speak
Challenge Rating 3
The nightmare can grant Resistance to Fire damage to a rider while it is on the nightmare.
The nightmare sheds Bright Light in a 10-foot radius and Dim Light for an additional 10 feet.
Melee Attack Roll: +6, reach 5 ft. Hit: 13 (2d8 + 4) Bludgeoning damage plus 10 (3d6) Fire damage.
The nightmare and up to three willing creatures within 5 feet of it teleport to the Ethereal Plane from the Material Plane or vice versa.