Swarm of Obsidian Butterflies

You call forth a swarm of obsidian butterflies to protect you. They flit around you to a distance of 15 feet for the duration. An affected creature's speed is halved in the area, and when the creature enters the area for the first time on a turn or starts its turn there, it must make a Dexterity saving throw. On a failed save, the creature takes 3d8 slashing damage. On a successful save, the creature takes half as much damage.

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d8 for each slot level above 2nd