Ancient Wolf of the East.

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

Might makes Right. The Ancient Wolf is Colossal, taking up 6 x 6 squares, and has advantage on an attack roll against a creature if is Large or smaller. In addition, an adverse effect that the Ancient Wolf would suffer only lasts until the start of its turn.

Damage Threshold. The Ancient Wolf has outlived its peers. It is unaffected by damage that doesn't deal at least 10 points of damage.

Multiattack. The Ancient Wolf makes 3 Sweeping Claw Attacks., and can move an additional 20 ft. as part of each attack.

Sweeping Claw. Melee Weapon Attack: +12 to hit, all creatures within 10 ft of the target. Hit: 10 (8d6 + 6) piercing damage. If the target is a creature, it must succeed on a DC 18 Strength saving throw or be knocked prone.

Ancient Breath (Recharge 6). The Ancient Wolf exhales breath in a 60-foot cone, each creature must make a DC 21 Constitution saving throw, taking 8d8 cold damage on a failed save, or half as much damage on a successful one. In addition, a creature that fails its save by 5 or more ages by 1d4 x 10 years, and the Ancient Wolf regains that many years onto its life span, healing for the amount of years claimed.

The Ancient Wolf has 3 legendary actions.

Golden Sight. The Ancient Wolf forces a creature it can see to make a DC 21 Wisdom Saving throw. On a failure , the Ancient Wolf can make a 60 ft. leap without provoking opportunity attacks, and make a Claw Sweep attack against that creature.

Golden Speed. The Ancient Wolf forces a creature it can see to make a DC 21 Charisma Saving throw. On a failure, the Ancient Wolf moves up one space on the initiative tracker.

Golden Fangs. The Ancient Wolf forces a creature it can see to make a DC 21 Intelligence Saving throw. On a failure, the Ancient Wolf marks that creature. If the first attack the Ancient Wolf makes against that creature is a hit, it is considered a critical hit.