Cult of Haask, the Voice of Hargut

The cultist transforms into a Tiny, slug-like being and teleports onto the shoulder of a Humanoid that it can see within 30 feet of it. The targeted Humanoid must succeed on a DC 15 Charisma saving throw or be Charmed by the cultist. While the target is Charmed, the cultist has control of it on the target's next turn. At the end of that turn, the cultist teleports to an unoccupied space it can see within 30 feet of it and returns to its normal form. The cultist can't be targeted directly by any attack or other effect while it's in the slug-like form, but it is subject to areas of effect as normal.