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.