Cruc’Melion

Lich’s Phylactery: Cruc’Mel has undergone the ritual to achieve Lichdom and therefore has placed his soul in a phylactery. If you destroy Cruc’Mels body, he will regenerate at his phylactery after 1d4+4 days. After which he will fully regenerate his physical form.

Turn Resistance: Cruc’Mel has a powerful force of will, making it quite difficult to turn him in combat due to his undead nature. He has advantage on any spell or effect that turns undead creatures. 

Legendary Resistance (3/Day). If Cruc’Mel fails a saving throw, it can choose to succeed instead.

Spellcasting. Cruc’Mel is a 20th level spellcaster. His spellcasting ability is Intelligence (spell save DC 22, +14 to hit with spell attacks). Cruc’Mel has following Wizard spells prepared:
Cantrips (at will): Mage Hand, Prestidigitation, Toll the Dead.

1st level (4 slots): Detect Magic, Ray of Sickness

2nd level (3 slots): Crown of Madness, Hold Person

3rd level (3 slots): Animate Dead, Counterspell, Sleet Storm, Vampiric Touch

4th level (3 slots): Blight, Dimension Door, Ice Storm

5th level (2 slots): Cone of Cold, Gaes, Scrying

6th level (2 slots): Investiture of Ice, Soul Cage

7th level (1 slot): Finger of Death, Simulacrum

8th level (1 slot): Clone, Maddening Darkness

9th level (1 slot): Power Word Kill, Time Ravage 

Arcane Mastery: Cruc’Mel may recover 1 spell slot of his  choice as an action. If he recovers a 7th level spell or higher, he takes a number of d6’s in force damage equal to the spell slot level due to pulling upon great Magic’s and straining himself.

Winter’s End: Melee Weapon Attack: +14 to hit, reach 10 ft. 1 target. Hit: 22 (2d6 + 12) slashing damage and 22 (2d6 + 12) cold damage. The target on hit must make a DC 18 constitution saving throw or take an additional 22 (2d6 + 12) necrotic damage.

Cruc’Mel 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. Cruc’Mel regains spent legendary actions at the start of its turn.

Low Level Spell (Costs 1 Action). Cruc’Mel casts a spell from 1st-4th level. 

Winter’s End (Costs 1 Action). Cruc’Mel makes a weapon attack using his weapon, Winter’s End.

Grasp of the Lich Lord (Costs 2 Actions). Cruc’Mel makes a melee spell attack against the target. On hit he grapples the creature. At the start of each of the grappled creatures turns, the get 1 exhaustion stack. They may take a Dexterity (Acrobatics) or Strength (Athletics) check at the end of their turns to break out of the grapple.