The Watcher (5e Creature)
From D&D Wiki
Small fiend (devil), lawful evil
Skills Perception +4, Stealth +4, Sleight of Hand +4
Elusive Body. The Watcher can move through a space as narrow as 1 inch wide without squeezing.
Ethereal Sight. The ghost can see 60 feet into the Ethereal Plane when it is on the Material Plane, and vice versa.
Incorporeal Movement. The ghost can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn in side an object.
Devil's Sight. Magical darkness doesn't impede The Watcher's darkvision.
Magic Resistance. The Watcher has advantage on saving throws against spells and other magical effects.
Shadow Claw. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 2) necrotic damage.
Cold Touch (Recharge 5-6). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 16 (4d6 + 2) cold damage.
Conqueror of Souls. The Watcher initiates an Intelligence contest with a humanoid within 5 feet of it. If it wins the contest it occupies the target's body. While inside the target, The Watcher has total cover against attacks and other effects originating outside its host. It automatically succeeds on Insight checks made against the target, and has advantage on melee weapon attacks against the target. It can leave the host as a bonus action.
Invisibility. The Watcher turns invisible until it attacks or until its concentration ends (as if concentrating on a spell). Any equipment The Watcher wears or carries is invisible with it.
Etherealness. The ghost enters the Ethereal Plane from the Material Plane, or vice versa. It is visible on the Material Plane while it is in the Border Ethereal, and viae versa, yet it can't affect or be affected by anything on the other plane.
Possession (Recharge 6). One humanoid that the ghost can see within 5 feet of it must succeed on a DC 14 Charisma saving throw or be possessed by the watcher; the watcher then disappears, and the target is incapacitated and loses control of its body. The watcher now controls the body but doesn't deprive the target of awareness. The watcher can't be targeted by any attack, spell, or other effect, and it retains its alignment, Intelligence, Wisdom, Charisma, and immunity to being charmed and frightened. It otherwise uses the possessed target's statistics, but doesn't gain access to the target's knowledge, class features, or proficiencies.
The Watcher is evil and shadow taking shape. And they embrace it as part from them as the powers of the lord's they’re sworn to serve. Spiteful, fast-talking and cruel, he is nevertheless one of his lord’s most trusted servants. Empowered by them, The Watcher flagrantly tortures and humiliates his charges, dripping poisonous insults and sarcasm onto their prostrate forms. When The Watcher captures a soul he never leaves it, and then The Watcher jumps at the chance to lay you low. Nevertheless The Watcher is not without ambitions, they are more then willing to cheat, betray and kill any and all even their masters if that is what it takes to get what they want. It is more of a proof that even demons should be careful what they wish for . . .