Sources
CR
Type
Size
Alignment
Movement

Alhoon

Medium Undead, Lawful Evil

Armor Class 15 (natural armor)
Hit Points 120 (16d8 + 48)
Speed 30 ft.
STR
11
+0
DEX
12
+1
CON
16
+3
INT
19
+4
WIS
17
+3
CHA
17
+3
Saving Throws CON +7, INT +8, WIS +7, CHA +7
Skills Arcana +8, Deception +7, History +8, Insight +7, Perception +7, Stealth +5
Damage Resistances cold, lightning, necrotic
Damage Immunities poison; bludgeoning, piercing, slashing, from nonmagical attacks
Condition Immunities Charmed, Exhaustion, Frightened, Paralyzed, Poisoned
Senses truesight 120 ft., passive Perception 17
Languages Deep Speech, Undercommon, telepathy 120 ft.
Challenge 10 (5,900 XP)

Traits

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

Turn Resistance. The alhoon has advantage on saving throws against any effect that turns undead.

Spellcasting

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

At will: detect thoughts, levitate

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

Spellcasting. The alhoon is a 12th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 16, +8 to hit with spell attacks). The alhoon has the following wizard spells prepared:

Cantrips (at will): chill touch, dancing lights, mage hand, prestidigitation, shocking grasp

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

2nd level (3 slots): invisibility, mirror image, scorching ray

3rd level (3 slots): counterspell, fly, lightning bolt

4th level (3 slots): confusion, Evard's black tentacles, phantasmal killer

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

6th level (1 slot): disintegrate, globe of invulnerability

Actions

Chilling Grasp. Melee Spell Attack: +8 to hit, reach 5 ft., one target. Hit:10 (3d6) cold damage.

Mind Blast (Recharge 5–6). The alhoon magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 16 Intelligence saving throw or take 22 (4d8 + 4) psychic damage and be stunned for 1 minute. A target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Lore

Mind flayers that pursue arcane magic are exiled as deviants, and for them no eternal communion with an elder brain is possible. The road to lichdom offers a way to escape the permanency of death, but that path is long and solitary. Alhoons are mind flayers that use a shortcut.