Cecaelian

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

Water Vulnerabilities. Cecaelian's are Vulnerable to Thunder damage when in water (or "wet"), or Lightning damage when out of it.

Innate Spellcasting (Psionics). The Cecaelian innate spellcasting ability is Wisdom (spell save DC 16). It can innately cast the following spells, requiring no components:

At will: acid arrow, levitate

1/day each: clone, plane shift (self only)

1/long rest true polymorph

Spellcasting. The Cecaelian is a 10th-level spellcaster. Its spellcasting ability is Wisdom (save DC 16, +7 to hit with spell attacks). The Cecaelian has the following wizard spells prepared:

Cantrips (at will): blade ward, dancing lights, mage hand, shocking grasp

1st level (4 slots): detect magic, disguise self, shield, sleep

2nd level (3 slots): blur, invisibility, ray of enfeeblement

3rd level (3 slots): clairvoyance, lightning bolt, sending

4th level (3 slots): confusion, hallucinatory terrain

5th level (2 slots): telekinesis, wall of force

Tentacles. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 15 (2d10 + 4) psychic damage. If the target is Medium or smaller, it is grappled (escape DC 16) and must succeed on a DC 16 Wisdom saving throw or be stunned until this grapple ends.