Cosmo Wolf

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.  Bites and if the bite hits the Cosmo Wolf tosses the creature 15ft and uses Fire breaking Howl

Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 15 (4d8 + 6) piercing damage. If the target is a creature, it must succeed on a DC 18 Strength saving throw or be knocked prone.

Claw. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) slashing damage. If the target is a creature, it must succeed on a DC 19 Strength saving throw or be knocked prone.

Fire Breaking 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 Fire 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.

Furious Bite (Costs 2 Actions). Cosmo wolf makes one Bite attack. If the target is a Huge or smaller creature, it is grappled (escape DC 20) and is restrained until this grapple ends. Cosmo Wolf can have only one creature grappled this way at a time.

Furious Claw swipes  (Costs 3 Actions). This is Three claw attack in  the same action. 

When the Cosmo Wolf reaches 20% of hp lift 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.

Mass Heal (Costs 2 Actions). Range 60 Ft. A flood of healing energy flows from you into injured creatures around you. You restore up to 300 hit points, divided as you choose among any number of creatures that you can see within range. Creatures healed by this spell are also cured of all diseases and any effect making them blinded or deafened. but cannot heal self  This spell has no effect on undead or constructs

Cosmo-Shattering Howl (Costs 3 Actions). Range 150 Ft. A howl loud enough to split the clouds. A storm made up of sheets of roaring flame appears in a location you choose within range. The area of the storm consists of up to ten 10-foot cubes, which you can arrange as you wish. Each cube must have at least one face adjacent to the face of another cube. Each creature in the area must make a Dexterity saving throw. It takes 8d10 fire damage on a failed save, or half as much damage on a successful one.

The fire damages objects in the area and ignites flammable objects that aren't being worn or carried. If you choose, plant life in the area is unaffected by this action.