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

Meditation (Recharges after a Short or Long Rest). If Nimzo would be reduced to 0 hit points, his current hit point total instead resets to 355 hit points, he recharges all abilities, and regains any expended uses of Legendary Resistance. Additionally, Nimzo can now use the options in the “Mythic Actions” section for 1 hour and the Desperate Attack Action, and can no longer use the Multiattack and Claws action for that hour. Award a party an additional 50,000 XP (100,000 XP total) for defeating Nimzo after Meditation activates.

Multiattack. Nimzo attacks twice with his Claws

Claws. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 41 (6d10 + 8) force damage.

Desperate Attack. (Mythic Only) Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 107 (18d10 + 8) force damage. This attack does not do extra damage on a Critical Hit.

Disruptive Wave (Recharge 6). Nimzo causes the concentration of all creatures within 100 feet of him to be broken. 

Kaboom (Recharge 6). Nimzo magically conjures a immense explosion of light particles centered on a point he can see within 120 feet of him. Each creature in a 30-foot-radius sphere centered on that point must make a DC 23 Dexterity saving throw, taking 35 (10d6) bludgeoning damage and 35 (10d6) radiant damage on a failed save, or half as much damage on a successful one.

Kasap (Recharge 5-6). Nimzo drains the defensive power of his enemies. All creatures of Nimzo's choice within 60 feet of him gain Vulnerability to all damage types until the end of Nimzo's next turn.  

Scorch Breath (Recharge 6). Nimzo spews forth blazing fire in a 60-foot cone. Each creature in that area must make a DC 24 Dexterity saving throw, taking 77 (14d10) Fire damage on a failed save, or half as much damage on a successful one.

Nimzo can take 2 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. Nimzo regains spent legendary actions at the start of his turn.

Attack. Nimzo attacks once with his Claws.

Kaboom (Costs 2 Actions). Nimzo uses Kaboom if it's recharged. 

If the Nimzo's Meditation trait has activated in the last hour, he can use the options below as legendary actions.

Kafrizzle (Recharge 5-6) (Costs 2 Actions). Ranged Spell Attack: +14 to hit, range 60 ft., one target. Hit: 88 (16d8+16) fire damage.