Innate Spellcasting. Graz'zt's spellcasting ability is Charisma (spell save DC 24). Demogorgon can innately cast the following spells, requiring no material components:
Shapechanger. Graz'zt can use his action to polymorph into a form that resembles a Medium humanoid, or back into his true form. Aside from his size, his statistics are the same in each form. Any equipment he is wearing or carrying isn't transformed. Demonic Awakening (Recharges after a Short or Long Rest). If Graz'zt would be reduced to 0 hit points, his current hit point total instead resets to 326 (80% of his maximum hit points) hit points, he regains any expended uses of Legendary Resistance. Additionally, he can now use the options in the "Mythic Actions" section for 1 hour. Legendary Resistance (4/Day). If Graz'zt fails a saving throw, he can choose to succeed instead. Magic Resistance. Graz'zt has advantage on saving throws against spells and other magical effects. Magic Weapons. Graz'zt's weapon attacks are magical.
Multiattack. Graz'zt attacks twice with Wave of Sorrow. Wave of Sorrow (Greatsword). Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 20 (4d6 + 6) slashing damage plus 10 (3d6) acid damage. Teleport. Graz'zt magically teleports, along with any equipment he is wearing or carrying, up to 120 feet to an unoccupied space he can see.
Graz'zt 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. Graz'zt regains spent legendary actions at the start of his turn. Attacks. Graz'zt attacks once with Wave of Sorrow. Dance, My Puppet! One creature charmed by Graz'zt that Graz'zt can see must use it's reaction to move up to it's speed as Graz'zt directs. Sow Discord. Graz'zt casts crown of madness or dissonant whispers. Teleport. Graz'zt uses his teleport action.
On Initiative count 20 (losing initiative ties), Graz'zt can take a lair action to cause one of the following effects: he can't use the same effect two rounds in a row:
Graz'zt's lair is his Argent Palace.