Sources
CR
Type
Size
Alignment
Movement

Oneirovore

Large Fiend, Unaligned

Armor Class 19 (natural armor)
Hit Points 237 (19d10 + 133)
Speed 20 ft.
STR
16
+3
DEX
12
+1
CON
25
+7
INT
12
+1
WIS
10
+0
CHA
10
+0
Saving Throws CON +11, INT +5
Skills Insight +4, Nature +5, Perception +4, Survival +4
Damage Resistances fire, poison; bludgeoning, piercing, slashing, from nonmagical attacks that aren't silvered
Damage Immunities psychic
Condition Immunities Blinded, Charmed, Frightened
Senses truesight 60 ft., passive Perception 14
Languages
Challenge 11 (7,200 XP)

Actions

Stomp. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit:16 (2d12 + 3) force damage.

Realize Nightmares (Recharge 4–6). The oneirovore manipulates the perception of nearby creatures, sending them into a panic. Creatures of the oneirovore's choice that it can see within 60 feet must make a DC 19 Charisma saving throw. On a failed save, the creature has the charmed condition, their vision distorted such that they view their allies as creatures of pure fear and hatred. While charmed, a creature will use their actions to attack their allies with intent to kill. A charmed creature may repeat the saving throw at the end of each turn, ending the effect on a success.

Warning Cry (1/Day). The oneirovore lets out an earsplitting shriek, calling for infernal reinforcements. Creatures that are not Fiends that are within 120 feet of the oneirovore must make a DC 19 Constitution saving throw, taking 55 (10d10) thunder damage on a failed save, or half as much damage on a successful one. Any lesser devils within a 1-mile-radius, centered on the oneirovore, are required by contract to come to its aid upon hearing its Warning Cry. Higher ranking devils may investigate if they desire, but the call holds no magical sway over them.

Lore

The ancestors of these Fiends were servants of the divine and Fey which devoured the nightmares of mortals, bringing restful sleep. Imported into the Nine Hells and cultivated by devils, dream eaters, as they're also known, became a powerful weapon in subtly corrupting mortal minds. They can be found grazing wherever the toxic foliage of the Nine Hells grows, often guarded by low-status devils and hell hounds. When brought to weak points between the planes, their spirits seep into the mortal…