Arion Ascended

Spellcasting: Arion is a 20th-level spellcaster. Its spellcasting ability is Intellegence (spell save DC 21, +13 to hit with spell attacks). Arion has following Wizard spells prepared:
Cantrips (at will): frostbite, chill touch

1. level (4 slots): feather fall, magic missile, shield
2. level (3 slots): Misty Step, Tasha's Mind Whip
3. level (3 slots): fireball, dispel magic, counterspell, slow
4. level (3 slots): banishment, fire shield
5. level (2 slots): dominate person, steel wind strike
6. level (2 slot): disintegrate, Arions Heater
7. level (2 slot): Forcecage, Prismatic Spray
8. level (1 slot): Incendiary Cloud
9. level (1 slot): Invunerability

Master Spellcaster: Arion has advantage on concentration checks

Dual Soul and mind: Arion can concentrate on two Spells at once.

Adamantine Coating: Any critical hits against him, become normal hits.

Undead vitality: Arion gains 10 Hitpoints at the beginning of each of his turn.

Firery Engine: Every time Arion takes damage he is immune to, he gains that many engine Points. He also gets 10 Engine Points at the beginning of each of his turns.

Multiattack: Arion can attack twice with his flametongue, or four times with his shadow spear.

Flametongue: Melee Weapon Attack: +13 to hit, reach 10 ft., 1 target. Hit: 19 (4d6 + 5) fire damage.

Shadow spear: Ranged Weapon Attack: +13 to hit, range 18/36 m, 1 target. Hit: 13 (2d6 + 6) force damage.

Firery Engine: Arion can expand Engine Points, to activate abilities, lasting util the end of his turn:

Burn Up (40): Arion gains an additional action.

Heating (10): All creatures within a 9m (30ft.) radius sphere have to make a constitution save, or take 2d6 fire damage.

Hot to the touch (30): Arions melee attacks do an extra 3d8 damage, and every creature that attacks him with a melee attack take 3d8 damage.

Pyrotechnical explosion (50): Every creatures within a 27m (90ft.) radius sphere has to succeed on a Dexterity saving throw or take 8d6 fire damage.

Arion has 3 legendary action, wich he can use at the end of a players turn, he regains all expended legendary actions at the beginning of his turn.

Attack (1 Action). Arion makes a melee or ranged attack against a target within range.

Cantrip (1 Actions). Arion uses one of his Spells from level 0-5

Arion has 1 Mythic action, and can use it at the beginning of a players turn.

Spell (1 Actions). Arion casts one of his spells

Multiattack (1 Actions). Arion uses his multiattack.