Vortex Summoning

A giant vortex is summoned, causing all creatures within its grasp to fly around. Each creature within a 30 ft. radius must take a DC 19 Charisma check. On a success, they manage to anchor themselves. On a failure, they begin to fly around in the vortex. They take 2d8+5 bludgeoning damage, and then they roll a d20, but only if there are other creatures in the vortex. If the d20 lands on a number that is equal to or less than the number of creatures in the vortex, then a random creature is chosen from the ones in the vortex, excluding the creature who is currently being damaged. Both the random creature and the first creature take 2d4 + the other creature's armor class in bludgeoning damage.