If the target is medium or smaller, they are grappled. Escape DC 12.

Psychic damage. Range 6. Mind killer is invisible to the target until the end of the mind killer's next turn.

A Humanoid grappled by the mind killer must succeed on a DC 12 Strength saving throw or the mind killer enters the Humanoid's body. While inside a Humanoid, the mind killer has total cover against attacks and other effects originating outside the Humanoid, and the only action the mind killer can take is to leave the body, exiting in an unoccupied space within 5 feet of the body.

When a Humanoid ends their turn with the mind killer inside of them, they must succeed on a DC 13Constitution saving throw or take 10 necrotic damage. If the Humanoid is reduced to 0 hit points, they die and the mind killer takes over the body, which regains hit points equal to the Humanoid's hit point maximum. The mind killer retains their Intelligence, Wisdom, and Charisma scores, their understanding of Deep Speech and Undercommon, and their telepathy. They otherwise adopt the target's statistics and can take the actions the creature could take. They know everything the creature knew, including spells, class features, traits, and languages. If the body is reduced to 0 hit points after the mind killer takes control, the mind killer must leave it.

A creature wielding a sharp tool or weapon within reach of a Humanoid host or body with a mind killer inside can use an action to attempt to remove the mind killer, making an attack roll against the Humanoid's AC if the host is unwilling. On a hit, the creature deals 11 (2d10) slashing damage to the host and must make a DC 15 Wisdom (Medicine) check. On a successful check, the creature cuts the mind killer out of the host. On a faiIed check, if this slashing damage reduced the host to 0 hit points, the mind killer kills the host; otherwise, there is no effect.