The nightmare can grant resistance to fire damage to anyone riding it.
The nightmare sheds bright light in a 10-foot radius and dim light for an additional 10 feet.
Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage plus 7 (2d6) fire damage.
The nightmare and up to three willing creatures within 5 feet of it magically enter the Ethereal Plane from the Material Plane, or vice versa.