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

Spellcasting. Zaux is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 20, +12 to hit with spell attacks). Zaux has the following wizard spells prepared:

Cantrips (at will): mage hand, prestidigitation, mind sliver

1st level (4 slots): charm person, magic missile, shield, sleep

2nd level (3 slots): calm emotions, detect thoughts, hold person, invisibility

3rd level (3 slots): major image, counterspell, dispel magic, suggestion

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

5th level (3 slots): dominate person, geas, modify memory, telekinesis

6th level (2 slots): disintegrate, globe of invulnerability

7th level (1 slot): forcecage, project image

8th level (1 slot): feeblemind, power word stun

9th level (1 slot): power word kill, weird

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

Innate Spellcasting (Psionics). Zaux’s innate spellcasting ability is Intelligence (spell save DC 20). It can innately cast the following spells, requiring no components.

At will: detect thoughts, levitate

1/day each: antipathy/sympathy, mirage arcane

Paralyzing Touch. Melee Spell Attack: +12 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.

Tentacles. Melee Weapon Attack: +12 to hit, reach 15 ft., one creature. Hit: 27 (4d10 + 5) psychic damage. If the target is Large or smaller, it is grappled(escape DC 17) and must succeed on a DC 20 Intelligence saving throw or be stunned until this grapple ends.

Extract Essence. Melee Weapon Attack: +12 to hit, reach 5 ft., one incapacitated humanoid grappled by Zaux. Hit: 55 (10d10) psychic damage. If this damage reduces the target to 0 hit points, Zaux kills the target by extracting and devouring its essence.

Mind Blast (Recharge 5–6). Zaux magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 18 Intelligence saving throw or take 31 (4d12 + 5) 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.

Zaux gains the following legendary action options.

Tentacles. Zaux makes one attack with its tentacles.

Extract Essence (Costs 2 Actions). Zaux uses Extract Essence.

Mind Blast (Costs 3 Actions). Zaux recharges its Mind Blast and uses it.

Cast Spell (Costs 1–3 Actions). Zaux uses a spell slot to cast a 1st-, 2nd-, or 3rd-level spell that it has prepared. Doing so costs 1 legendary action per level of the spell.