Corrupted Phantasm

Ethereal Sight. The phantasm can see 60 feet into the Ethereal Plane when it is on the Material Plane, and vice versa.

Incorporeal Movement. The phantasm 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.

Withering Touch. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 17 (4d6 + 3) necrotic damage.

Etherealness. The phantasm 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 vice versa, yet it can't affect or be affected by anything on the other plane.

Dreadful Visage. Each non-undead creature within 60 feet of the phantasm that can see it must succeed on a DC 13 Wisdom saving throw or be frightened for 1 minute. If the save fails by 5 or more, the target also takes 17 (2d6 + 3) psychic damage, filling them with thoughts of existential dread and futility and instead becomes charmed. A frightened or charmed target can repeat the saving throw at the end of each of its turns, ending the frightened or charmed condition on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to this phantasm's Dreadful Visage for the next 24 hours. 

Possession (Recharge 6). One humanoid that the phantasm can see within 5 feet of it must succeed on a DC 13 Charisma saving throw or be possessed by the phantasm; the phantasm then disappears, and the target is incapacitated and loses control of its body. The phantasm now controls the body but doesn't deprive the target of awareness. The phantasm can't be targeted by any attack, spell, or other effect, except ones that turn undead, 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. If the target remains charmed for more than 3 rounds, they gain an Indefinite Madness

The possession lasts until the body drops to 0 hit points, the phantasm ends it as a bonus action, or the phantasm is turned or forced out by an effect like the dispel evil and good spell. When the possession ends, the phantasm reappears in an unoccupied space within 5 feet of the body. The target is immune to this phantasm's Possession for 24 hours after succeeding on the saving throw or after the possession ends.