Charge. If the abyssal centaur moves at least 30 feet straight toward a target and then hits it with a mace attack on the same turn, the target takes an extra 10 (3d6) bludgeoning damage.

Fear Aura. Any creature hostile to the abyssal centaur that starts its turn within 20 feet of the it must make a DC 10 Wisdom saving throw, unless the abyssal centaur is incapacitated. On a failed save, the creature is frightened until the start of its next turn. If a creature's saving throw is successful, the creature is immune to the abyssal centaur's Fear Aura for the next 24 hours.

Innate Spellcasting. The abyssal centaur's spellcasting ability is Charisma (spell save DC 12). The abyssal centaur can innately cast fireball, requiring no material components. 

Multiattack. The abyssal centaur makes two attacks: one with its mace or claw and one with its hooves. 

Mace. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 15 (2d6 + 8) bludgeoning damage. 

Hooves. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage.

Claw. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 17 (2d8 + 8) slashing damage.