Death of Obsidian Butterflies

You conjure a cloud of obsidian butterflies that fly out from your hands, cutting nearly everything to ribbons in their path. Buildings and the like are not destroyed but are heavily damaged from thousands of cuts but anything less sturdy is usually destroyed, like ropes or flesh. Each creature in the path of the butterflies must make a Dexterity saving throw. On a failed save a target takes 6d6 points of slashing damage and half as much damage on a successful one. The true insidious nature of the spell, however, lies in what happens after. The butterflies do not disappear, leaving a razor sharp blanket of wings on the ground unless dispelled or until the next sunrise touches them. Anyone walking on these butterflies without metal shoes automatically suffers (caster's level/2) slashing damage.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.