Defile

Defile the land beneath a creature within range.  Any time a creature enters this area for the first time or ends their turn within it, they must make a Dexterity saving throw or suffer 1d10 necrotic damage plus your spellcasting modifier.  The area is a 15-foot circle on the ground. Each time a creature takes damage from this effect the circle grows by an additional 10 feet.

At higher levels: Damage increases by 1d10 for each spell slot used above 2nd.