Baku

Fog of Dreams. The baku emanates a dream mist from its snout, creating a small fog around itself. Creatures that would normally be unaffected or immune to magical or nonmagical sleep are affected by such spells and effects while within 120 ft. of the baku. 

Incorporeal Movement. The baku can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

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

Slam. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 2) bludgeoning damage. 

Spellcasting (Innate). The baku’s spellcasting ability is Wisdom (spell save DC 15). It can cast the following spells innately: 
At will: sleep(9th level), dream
1/day each: plane shift(self only), invisibility(self only)

Restful Fog. The baku can expand the influence of its dream fog to even greater distances. As an action, the baku can greatly increase the effect of its Fog of Dreams feature, affecting all creatures in a 5 mile radius. Creatures caught within the expanding fog bank must make a DC 15 Wisdom saving throw or fall unconscious for the duration. The fog lasts indefinitely until dispelled at the source, the baku is incapacitated, or chooses to drop concentration (as if dropping concentration on a spell). Any creatures that enter the fog bank after it has been released are unaffected by this effect.

Roiling Nightmare (Recharge 5-6). The baku releases all of the nightmares it has consumed in a roiling torrent of dark dream energy within a 30-foot cone. Each creature in the cone must make a DC 15 Wisdom saving throw. On a failed save, the creature takes 27 (6d8) psychic damage and becomes frightened for 1 minute. On a successful save, the creature takes half the damage and is not frightened.