Aries

Thick hide. Finesse and thrown weapons have disadvantage to hit.

Beserker. The Aries is in a constant rage status, making it imune to being charmed, but more susceptible to falling prone.

Holy Aura. Infernal creatures immediately become frightened upon seeing Aries. They must succeed in a WIS saving throw (DC 10) in order to be cured of the condition.

Aspect of Mars. When Aries is hit by fire damage, they heal the equivalent of the damage the fire attack deals.

Word of the Ancient. Aries speaks in a language only understood by those touched by the outer planes. Any creature outside this category must make a Wisdom saving throw (DC 12). Those that fail become frightened.

Roar. The Aries lets out a manic scream, making any opponent do a WIS saving throw, becoming frightened if unsuccessful. (DC 13)

Charge. The Aries takes one turn to focus on a target and run forward, bashing its head against the target in the next. If interrupted, the Aries falls prone. (Attack: +5 to hit, range 5 ft., 1 target. Hit: 2d8 bludgeoning damage). 

Stomp. The Aries stomps viciously on the ground, making every target within range do a dexterity saving throw, talking half the damage if successful. (Attack: +5 to hit, range 20 ft. cube, Hit: 2d6 bludgeoning damage, DC saving throw: 13).

Bite. The Aries uses its powerful jaws to bite down on a target. (Attack: +5 to hit, range 5 ft., 1 target. Hit: 1d6+3 piercing damage)

Bucking kick. If attacked from behind, the Aries deals a vicious kick towards the attacker. (Attack: +3 to hit, range 5 ft., Hit: 2d4 bludgeoning damage, launches target 10 ft. If successful.)