Anguisher

Amorphous. The anguisher can move through a space as narrow as 1 inch wide without squeezing.

Continued Suffering. A creature that has an Intelligence score of 4 or higher and dies from an anguisher’s attacks spawns a new anguisher in 3 days. Any effect that prevents the body from becoming undead also prevents the emergence of the new anguisher.

Frightening Advantage. The anguisher has advantage on attack rolls against creatures that are frightened. Against such targets, the anguisher scores a critical hit on a roll of 18 to 20.

Multiattack. The anguisher uses anguish twice.

Anguish. Melee or Ranged Spell Attack: +5 to hit, reach 5 ft. or range 60 ft., one creature. Hit: 13 (3d6 + 3) psychic damage, and the target is frightened of the anguisher and must use its reaction to move its speed away by the safest possible route. Movement used during this reaction can’t be used during the target’s turn.

Harrow (Recharge 6). Each creature of the anguisher’s choice within 60 feet and aware of the anguisher must make a DC 13 Wisdom saving throw. On a failure, a creature takes 17 (5d6) psychic damage and becomes frightened for 1 minute. If the save succeeds, the creature takes half the damage and isn’t frightened. A frightened creature can repeat the saving throw at the end of each of its turns, ending the condition on itself on a success.

Invisibility. The anguisher magically turns invisible until it attacks or until its concentration ends (as if concentrating on a spell).