Aragorn

Keen Hearing and Smell. Aragorn has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Charge. If the rhinoceros moves at least 30 feet straight toward a target and then hits it with a gore attack on the same turn, the target takes an extra 9 (2d8) bludgeoning damage. If the target is a creature, it must succeed on a DC 15 Strength saving throw or be knocked Prone.

Aragorn's saddle. Aragorn wears a saddle that allows him to be mounted. It takes an action to mount him within a touch range, and if the rider takes more than 20 damage or Aragorn more than 30 the rider is knocked off and prone. While riding the rider gains+1 AC and Aragorn gains +2 AC.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 5) piercing damage. If the target is a creature, it must succeed on a DC 13 Strength saving throw or be knocked prone.

Gore. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) bludgeoning damage.

 Acid Breath (Recharge 5–6). Aragorn exhales acid in a 15-­foot line that is 5 feet wide. Each creature in that line must make a DC 12 Dexterity saving throw, taking 16 (4d8) acid damage on a failed save, or half as much damage on a successful one.