Artisan of Kozilek

Innate Spellcasting. Artisan of Kozilek's innate spellcasting ability is Wisdom (spell save DC 20). He can innately cast the following spells, requiring no material components:

At will: Lightning Bolt (5th level spell slot)
3/Day: Chain Lightning
1/Day: Call Lightning (6th level spell slot)

Corpse Vision. Artisan of Kozilek can see all corpses within 500 feet of him, regardless of if they are within line of sight or not. (It can see them through earth, stone, metal, etc)

Alien Mind. Artisan of Kozilek has advantage on Wisdom saving throws.

Master of Lightning. Artisan of Kozilek has advantage on Constitution saving throws made on concentration checks for spells that deal lightning damage.

Legendary Resistance (3/Day). If Kozilek fails a saving throw, he can choose to succeed instead.

Multiattack. Artisan of Kozilek make four fist attacks.

Fist. Melee Weapon Attack: +13 to hit, reach 20 ft., one target. Hit: 21 (2d12 + 7) bludgeoning damage and 21 (2d12 + 7) lightning damage.

Enervating Scream (Recharge 5–6). Artisan of Kozilek lets out a scream that disperses lightning in a 90-­foot radius circle around it:

• Each non-undead creature in that circle must make a DC 20 Dexterity saving throw, taking 36 (6d10) lightning damage, 36 (6d10) necrotic damage and being knocked prone on a failed save, or half as much damage on a successful one.
• Each undead creature in that circle heals for 18 (3d10) hit points and can use its reaction to make an attack on a creature within range.
• If there are corpses within that circle that are Huge or smaller, they are put into a state of undeath. This creature is undead and has half its average starting health, -2 AC and +10 bonus movement. It is immediately hostile to anything Artisan of Kozilek is hostile towards and will attack them mindlessly.

Artisan of Kozilek 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. Artisan of Kozilek regains spent legendary actions at the start of his turn.

Hit and Run. Artisan of Kozilek makes one Fist attack and can move up to half its movement speed without provoking an attack of opportunity.

Jolting Performance (Costs 2 actions). Artisan of Kozilek casts a spell using his Innate Spellcasting ability. Alternatively, if it is concentrating on a spell, it can chose to move it as though it was using the spells bonus action interaction.

Gruesome Encore (Costs 3 actions). Artisan of Kozilek selects one Gargantuan or Huge corpse, 2 Large corpses or 4 medium corpses within 150 feet and returns them to a state of undeath. These creature are undead and have half their average starting health, -2 AC and +10 bonus movement. They are immediately hostile to anything Artisan of Kozilek is hostile towards and will attack them mindlessly. (Roll the initiatives of the 1, 2 or 4 monsters as a group).