Medium aberration, neutral evil
Armor Class: 17
Hit Points: 153 (18d8 + 72)
Damage Resistances: bludgeoning, piercing and slashing from nonmagical attacks
Damage Immunities: psychic
Condition Immunities: blinded, charmed, frightened
Senses: blindsight 120ft, passive Perception 17
Languages: Common, Deep Speech, Telepathy 120 ft.
Challenge Rating: 14
The Descender Priest's innate spellcasting ability is Intelligence (spell save DC17). The Descender Priest can innately cast the following spells, requiring no material components:
1/day: confusion, eyebite
3/day: charm person, detect magic, detect thoughts, suggestion
Legendary Resistance (3/day)
If the Descender Priest fails a saving throw, it can choose to succeed instead.
The Descender Priest can use its action to polymorph into a Small or Medium humanoid, or back into its true form. Other than its size and speed, its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.
The Descender Priest makes three tendril attacks. The first of these attacks that hit each round deals an extra 26 (4d12) psychic damage to the target. Included in the attack below.
Melee Weapon Attack: +7 to hit, range 20 ft., one target. Hit 11 (2d8 + 2) bludgeoning damage, and the target must make a DC17 Wisdom saving throw, taking 26 (4d12) psychic damage on a failed save, or half as much damage on a successful one.
Summon Descender Spawn (Recharge 6)
The Descender Priest summons a Descender Spawn which materializes within 30 feet of it in an unoccupied space it can see. The Descender Span vanishes when it drops to 0 hit points or when its summoner dies.
The Descender Priest 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. The Descender Priest regains spent legendary actions at the start of its turn.
The Descender Priest moves up to its speed without provoking opportunity attacks.
The Descender Priest uses its Tendril attack.
Wailing Insanity (Costs 3 Actions)
The Descender Priest lets out an otherworldly wail. Any non-aberration within 120 feet of the Descender Priest that can hear the wail must succeed on a DC17 Wisdom saving throw or gain 1 level of Insanity. Creatures affected in this way can only gain 3 levels of Insanity from an indvidiaul Descender Priest every 24 hours.