The Entity's Grasping Void

You draw on power from the Far Realms, and use it to call on power from an ancient entity. Tentacles are drawn through portals at a point you can see within range, grasping all creatures in a 30 feet radius. These creatures must make strength saving throws, becoming grappled and taking 5d10 psychic damage on a failed save. At the end of each of their turns, they can attempt to make another saving throw, taking an additional 2d10 psychic damage on a failed save, and ending the effects on themselves with a successful save.