Astral splash

spectral energy ripples out in a 40-foot-radius Sphere from a point you choose within range. Each creature in that area makes a Charisma saving throw, taking 10d4 Force damage and becoming ethereal for 1 round (as if affected by the Blink spell) on a failed save on a failed save or half as much damage on a successful one. If a creature fails this save by a number equal to or greater than a third of its CR (round up), it teleports to the astral plane.

Using a Higher-Level Spell Slot. The damage increases by 2d4 for each spell slot level above 6.