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

Bite. Melee Weapon Attack: +19 to hit, reach 12 ft., three targets. Hit: 401 (60d12 + 80) piercing damage. If the target is a creature, it must succeed on a DC 27 Strength saving throw or be knocked prone.

When Aarbrok, The Rainbow Wolf enters a light level of 7 or less, he gives off rainbow light.

Aarbrok, The Rainbow Wolf can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Aarbrok, The Rainbow Wolf regains spent legendary actions at the start of its turn. 

Bite. Aarbrok, The Rainbow Wolf makes one bite attack.

Charm. Aarbrok, The Rainbow Wolf attempts charm one target. Tat target must succeed on a DC24 Wisdom saving throw or be charmed.

GO SAVAGE!!!!! (Costs 2 Actions) Aarbrok, The Rainbow Wolf makes 5 bite attacks, all at the same target.