Wrath of Caiphon

You open a gateway to a world of purple fire that pulses as if it was alive, and is covered by a purple, amoebic ocean. A 20-foot-radius sphere of amoebic tentacles and purple flame appears, centered on a point with range and lasting for the duration. This void is filled with a cacophony of soft whispers and slurping noises that can be heard up to 30 feet away. Creatures fully within the area are poisoned.

The void creates a warp in the fabric of space, and the area is difficult terrain. Any creature that starts its turn in the area takes 2d6 fire damage. Any creature that ends its turn in the area must succeed on a Dexterity saving throw or take 2d6 acid damage as purple, otherworldly  amoebic tentacles rub against it.