Alien Mind. If a creature tries to read Zelrock's thoughts or deals psychic damage to it, that creature must succeed on a DC 22 Intelligence saving throw or be stunned for 1 minute. The stunned creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Innate Spellcasting. Zelrock’s spellcasting ability is Intelligence (spell save DC 24, +18 to hit with spell attacks). He can innately cast the following spells, requiring no material components:

At will: counterspell, detect magic, detect thoughts, dispel magic, eyebite, fireball, lightning bolt, shield, Misty Step

3/day each: chain lightning, create undead, dream, hold monster, mass suggestion, scrying, Dominate Person

1/day each: foresight, gate, power word kill, teleport, Dominate Monster

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

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

Master of Magic. Zelrock has advantage on Constitution saving throws to maintain concentration.

Multiattack. Sul Khatesh makes four attacks with Arcane Blast.

Arcane Blast. Ranged Spell Attack: +18 to hit, range 120 ft., one target. Hit: 15 (1d10 + 10) force damage.

Longsword. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 21 (5d8 + 8) slashing damage plus 13 (3d8) lightning damage. If Zelrock scores a critical hit, it rolls damage dice three times, instead of twice.

Psychic Ray. Zelrock shoots one of the following magical eye rays of its choice, targeting one creature it can see within 120 feet of it:

1. Psyche-Reconstruction Ray. The target must make a DC 22 Wisdom saving throw, taking 49 (9d10) psychic damage on a failed save, or half as much damage on a successful one. If this damage reduces a creature to 0 hit points, it dies and transforms into a spectator under Zelrock control and acts immediately after Zelrock in the initiative order. The target can’t be returned to its original form by any means short of a wish spell.

2. Domination Ray. The target must succeed on a DC 22 Wisdom saving throw or be charmed by Zelrock for 1 minute or until the target takes damage. Zelrock can issue telepathic commands to the charmed creature (no action required), which it does its best to obey.

3. Mind-Weakening Ray. The target must succeed on a DC 22 Intelligence saving throw or take 36 (8d8) psychic damage and be unable to cast spells or activate magic items 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.

4. Blinding Ray. The target and each creature within 10 feet of it must succeed on a DC 22 Constitution saving throw or take 19 (3d12) radiant damage and be blinded for 1 minute. Until this blindness ends, Zelrock can see through the blinded creature’s eyes. The blinded creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Zelrock can take 4 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. Sul Khatesh regains spent legendary actions at the start of her turn.

Attack. Sul Khatesh makes two attacks with her Arcane Blast

At-Will Spell. Zelrock casts one of his at-will spells.

Consume Magic (Costs 2 Actions). Zelrock targets a creature within 120 feet of her who is concentrating on a spell. The target must succeed on a DC 26 Constitution saving throw or its concentration is broken on the spell, and Sul Khatesh gains 5 temporary hit points per level of that spell.

Spellcasting (Costs 2 Actions). Zelrock casts a spell

Mind Blast (Costs 3 Actions). Dyrrn magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 23 Intelligence saving throw or take 30 (5d8 + 8) psychic damage and be stunned for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.