Wave of Decay

You conjure up a wave of deadly mushrooms that ripple out on an area within range. The area can be up to 30 feet long, up to 10 feet wide, and up to 10 feet tall. Each creature in that area must make a Dexterity saving throw. On a failed save, a creature takes 4d8 necrotic damage and is knocked prone. On a successful save, a creature takes half as much damage and isn’t knocked prone. The mushrooms then spread out across the ground and vanish.