Ardo, the otherworld goblin

Unrelenting Gluttony. The creature has immunity against being frightened, poisoned or petrified, it can also apparently consume any organic material without any detrimental effects.

I am Ardo: ardo can't be subject of spells that change its form

Extra Action. Ardo may make three actions of any kind per turn

Legendary Resistance (3/day). If Ardo fails a saving throw, he can choose to succeed instead.

Chomp. Melee Unarmed Attack: +10 to hit, reach 5 ft, one target. Hit: 12 (6d4) piercing damage when used to attack an opponent who is not prone; 24 (6d8) piercing damage when used against a prone target; Ardo regains health equal to the damage dealt in both cases

Crescent Sweep. Area Weapon Attack: each creature in a 10 ft cone in front of you  make a DEX Save with DC 18 or take 20 (3d8 + 8) necrotic damage and they fall prone or they take half damage and don't fall if they succed

Spear. Melee Weapon Attack: + 10 to hit, reach 10 ft., one target. Hit: 17(3d6 + 5) piercing damage or 20 (3d8 + 5) piercing damage if used with two hands to make a melee attack plus 15 (4d6 + 3) necrotic damage.

Misty Step (Recharge 5-6) (Briefly surrounded by silvery mist, you teleport up to 30 feet to an unoccupied space that you can see.)

Ardo can take 3 legendary actions. Only one legendary action option can be used at the end of another creature's turn. Ardo regains spent legendary actions at the start of its turn.

Misty Step (Briefly surrounded by silvery mist, you teleport up to 30 feet to an unoccupied space that you can see.)

Legendary Recovery. If  Ardo uses a reaction, he can choose to recover that reaction spending a legendary action.

Ardo can use 4 mythic actions per combat (using each one for a maximum of 1 time)

Obliterate. Toxic Emission. Each creature in a 15 ft cone in front of Ardo must make a DC 19 constitution save. On a failure the creature takes 30 (4d12 + 6) poison damage and becomes poisoned. On a success the creature takes half damage and is not poisoned.

Dominate. (basically dominate person in non spell form with CHA DC 18): You attempt to beguile a humanoid that you can see within range. It must succeed on a Wisdom saving throw or be charmed by you for the duration. If you or creatures that are friendly to you are fighting it, it has advantage on the saving throw. While the target is charmed, you have a telepathic link with it as long as the two of you are on the same plane of existence. You can use this telepathic link to issue commands to the creature while you are conscious (no action required), which it does its best to obey. You can specify a simple and general course of action, such as “Attack that creature,” “Run over there,” or “Fetch that object.” If the creature completes the order and doesn’t receive further direction from you, it defends and preserves itself to the best of its ability. You can use your action to take total and precise control of the target. Until the end of your next turn, the creature takes only the actions you choose, and doesn’t do anything that you don’t allow it to do. During this time you can also cause the creature to use a reaction, but this requires you to use your own reaction as well. Each time the target takes damage, it makes a new Wisdom saving throw against the spell. If the saving throw succeeds, the spell ends.

Conquer: blind song (similar to false hydra song for flavour) (basically he goes in non interruptable invisibility for 3 turns if a WIS Save DC 17 is not passed)

Anger: summon 1d8 + 2 angry goblin archers