Archlich

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

Magic Resistance. The archlich has Advantage on saving throws against spells and other magical effects.

Spirit Jar. If destroyed, the archlich reforms in 1d6 days if it has a spirit jar, reviving with all its Hit Points. The new body appears in an unoccupied space within the archlich’s lair.

Multiattack. The archlich makes four attacks, using Eldritch Burst or Paralyzing Touch in any combination.

Eldritch Burst. Melee or Ranged Attack Roll: +16, reach 5 ft. or range 120 ft. Hit: 47 (6d12 + 8) Force damage.

Paralyzing Touch. Melee Attack Roll: +16, reach 5 ft. Hit: 22 (4d6 + 8) Cold damage, and the target has the Paralyzed condition until the end of its next turn.

Rotten Sphere (Recharge 5-6). Constitution Saving Throw: DC 24, each creature in a 20-foot radius Sphere centered on a point the archlich can see within 150 feet. Failure: 35 (6d8 + 8) Acid, Necrotic, or Poison damage (archlich's choice), and the target has the Poisoned condition until the end of the archlich's next turn. Success: Half damage only.

Spellcasting. The archlich casts one of the following spells, requiring no Material components, and using Intelligence as the spellcasting ability (spell save DC 24):

At Will: Animate Dead, Banishment, Blindness/Deafness (level 4 version), Detect Magic, Detect Thoughts, Dispel Magic, Greater invisibility, Mage Hand, Prestidigitation
2/Day Each: Antimagic Field, Befuddlement, Disintegrate, Dominate Monster, Forcecage, Maze, Power Word Kill, Power Word Stun, Plane Shift, Scrying, Teleport

Protective Magic. The archlich casts Counterspell or Shield in response to the spell’s trigger, requiring no Material components, and using the same spellcasting ability as Spellcasting.

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature’s turn, the lich can expend a use to take one of the following actions. The lich regains all expended uses at the start of each of its turns.

Deathly Teleport. The archlich teleports up to 60 feet to an unoccupied space it can see, and each creature within 10 feet of the space it left takes 11 (2d10) Necrotic damage and has Disadvantage on the next saving throw it makes before the end of its next turn.

Disrupt Life. Constitution Saving Throw: DC 24, each creature that isn’t an Undead in a 20-foot Emanation originating from the archlich. Failure: 35 (10d6) Necrotic damage, and the target can’t regain Hit Points until the end of its next turn. Success: Half damage only. Failure or Success: The archlich can’t take this action again until the start of its next turn.

Frightening Gaze. The archlich casts Fear, requiring no Material components, and using the same spellcasting ability as Spellcasting. The archlich can’t take this action again until the start of its next turn.