Unhinged Rant

You go on an unhinged rant about a topic of your choice. All creatures within 20ft of you must make an INT saving throw. On a failed save, targets will take 3d6 psychic damage, and are stunned. Each turn afterwards, they can make the save again. If they fail, they take another 1d4 psychic damage. On a success, this deals half damage, and the target is not stunned.