Keen Hearing and Smell. The wolf has advantage on Wisdom (Perception) checks that rely on hearing or smell.
Pack Tactics. The wolf has advantage on attack rolls against a creature if at least one of the wolf's allies is within 5 feet of the creature and the ally isn't incapacitated.
Legendary Resistance (3/Day). If the Cosmo Wolf fails a saving throw, it can choose to succeed instead.
Cosmo Wolf can attack three times per turn. Starts with Wrath of Nature, then bites and if the bite hits the Cosmo Wolf tosses the creature 15ft and uses Earthbreaking Howl
Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 7 (4d8 + 6) piercing damage. If the target is a creature, it must succeed on a DC 18 Strength saving throw or be knocked prone.
Wrath of Nature. Casts wrath of nature spell at will, without needing to maintain concentration.
Earthbreaking Howl. An ear rupturing howl blasts from the Cosmo Wolf in a 60ft cone. Any creatures in the cone must make a DC18 Con save or take 8d10 thunder dmg or half as much on a successful save.
Chase Down. As a reaction instead of taking an attack of opportunity the Cosmo Wolf runs alongside the foe moving and cuts them off after 40 ft. of movement.
Disappointing Snarl. As a reaction from an enemy moving outside of the Cosmo Wolf's attack range it may let out a snarl, angry at the creatures cowardice. The creature must make a Wisdom saving throw DC 18 or take 4d4 psychic dmg and have disadvantage on its next attack.
The Cosmo 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. The Cosmo Wolf regains spent legendary actions at the start of its turn.
Bite and Toss. Cosmo Wolf bites a target and then tosses them 15ft in a direction of its choosing.
Summon Spirit Wolves (Costs 2 Actions). Summons three spirit wolves into battle.
Bolstering Howl (Costs 3 Actions). All remaining spirit wolves gain 10 hp and deal force damage instead of piercing.
When the Cosmo Wolf reaches 0 hp it revives with full hit points and gains new mythic actions described below.
Rampaging Fury. The Cosmo Wolf makes an attack against each creature within range at advantage.
Summons Greater Spirit Wolves (Costs 2 Actions). Summons six greater spirit wolves into battle.
Star-Shattering Howl (Costs 3 Actions). A howl loud enough to split the clouds. Casts Meteor Storm at 10th level (extra 10d6 fire and 10d6 bludgeoning).