Ciaran

Legendary Resistance (5/Day). If Ciaran fails a saving throw, it can choose to succeed instead.

Spellcasting. Ciaran is an 20th-level spellcaster. His spellcasting ability is Intelligence (spell save DC 22, +15 to hit with spell attacks). Ciaran  has the following wizard spells prepared:

Cantrips (at will): mage hand, prestidigitation, ray of frost

1st level (4 slots): , magic missile, shield, thunderwave, Ray of sickness

2nd level (3 slots): Blindness/Deafness, invisibility, mirror image, blur

3rd level (3 slots): animate dead, counterspell, dispel magic, fireball, slow, pulse wave

4th level (3 slots): blight, dimension door, gravity sinkhole]

5th level (3 slots): Antilife shell, Enervation, cone of cold

6th level (1 slot): disintegrate, globe of invulnerability

7th level (1 slot): finger of death, Delayed Blast Fireball, prismatic spray

8th level (1 slot): dominate monster, Maze

9th level (1 slot): power word kill

Turn Resistance. Ciaran has advantage on saving throws against any effect that turns undead.

Paralyzing Touch. Melee Spell Attack: +15 to hit, reach 5 ft., one creature. Hit: 10 (3d6) cold damage. The target must succeed on a DC 18 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Ciaran can take 5 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. Ciaran regains spent legendary actions at the start of his turn.

Cantrip. Ciaran casts a cantrip.

Spell (Costs 2 Actions). Ciaran casts a spell of first level or higher.

Paralyzing Touch (Costs 2 Actions). Ciaran uses its Paralyzing Touch.

Frightening Gaze (Costs 2 Actions). Ciaran fixes his gaze on one creature it can see within 10 feet of him. The target must succeed on a DC 18 Wisdom saving throw against this magic or become frightened for 1 minute. The frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to Ciaran's gaze for the next 24 hours.

Disrupt Life (Costs 3 Actions). Each non-undead creature within 20 feet of Ciaran must make a DC 18 Constitution saving throw against this magic, taking 21 (6d6) necrotic damage on a failed save, or half as much damage on a successful one.

Soul Shield (Mythic Trait; Recharges after a Short or a Long Rest). When Ciaran is reduced to 0 hit points, all souls of his court's members from across the planes rush to rejuvenate him one final time. Ciaran's hit points become 200 and he gains 100 temporary hit points. He gains 3 mythic actions and can use the following actions until he takes a short or a long rest:

Spell. Ciaran casts a spell.

Paralyzing Grasp (costs 2 actions). Ciaran uses his Paralyzing Touch twice.

Drain Life (costs 3 actions). Each non-undead creature within 20 feet of Ciaran must make a DC18 Constitution saving throw against this magic, taking 21 (6d6) necrotic damage on a failed save, or half as much on a successful one.

Ciaran heals for half the total damage he dealt this way (cumulative for each creature affected. If two creatures got hit for a total of 10 damage each, Ciaran will heal for 20)