Cenorgrimm, Demon Lord of Curiosity

Legendary Resistance (3/day). If Cenorgrimm would fail a saving throw, it can choose to succeed.

Magic Resistance. Cenorgrimm has advantage on saving throws against spells and other magical effects.

Curiosity Aura. All other creatures within 120ft of Cenorgrimm cannot perform any general action type that they had taken on their immediate previous turn, (e.g. Attack, Hide, Cast a Spell, Use an Object, etc.) unless they make a DC 22 Intelligence Saving throw to avoid it for the current turn. However, if they succeed, they also take a -14 penalty on their next saving throw against this aura.

Regeneration Aura. Cenorgrimm and its allies within 30ft recover 30 hitpoints at the beginning of Cenorgrimm's turn as long as he has at least 1 hitpoint.

Multiattack. Cenorgrimm uses one of Glimmer of Curiosity, Horn of Ruin, and Spellcasting. It can replace Horn of Ruin and/or Spellcasting with Glimmer of Curiosity.

Glimmer of Curiosity. Cenorgrimm places an orb into the air at a point within 60ft that crackles with energy. At the start of his next turn, it flies toward a hostile target (with priority decided by intelligence / distance) within 120ft, going around cover if there is an indirect path. The target makes a Constitution Saving throw (DC 22), taking (7d12)  damage on a failure, or half on a success. The damage type any of Cenorgrimm's choice that wasn't chosen yet on this or the previous round. The orbs can be attacked and destroyed before they strike. They are magical objects with an AC of 30, and 25 hit points and succeed all saving throws.

Horn of Ruin. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) piercing damage, plus 39 (6d12) radiant or necrotic damage (Cenorgrimm's choice). Cenorgrimm can move up to its speed before or after this attack, without provoking attacks of opportunity.

Spellcasting. The archmage is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 22, +12 to hit with spell attacks).

Cantrips (at will): fire bolt, light, mage hand, prestidigitation

1st level (4 slots): detect magic, identify

2nd level (3 slots): detect thoughts, mirror image, misty step

3rd level (3 slots): counterspell, fly,

4th level (3 slots): banishment, fire shield, freedom of movement*

5th level (3 slots): cone of cold, scrying, wall of force,arcane hand, mislead

6th level (2 slot): disintegrate

7th level (1 slot): teleport

8th level (1 slot): mind blank*

9th level (1 slot): time stop

Cenorgrimm takes 2 legendary actions each round, which are refreshed at the start of his turn.

Strike. Cenorgrimm uses Glimmer of Curiosity or Horn of Ruin.

Restoration. The effects of Cenorgrimm's Regeneration Aura immediately trigger. This action cannot be taken again until the start of Cenorgrimm's turn.