Bladewire

You imbue the material component of this spell with magic and drop it or place it where desired. When a hostile creature steps over it or otherwise enters its space, the material animates, rising and spinning rapidly and with sufficient force that the wire or string will cause deep and severe wounds if struck. 

The target must make a DC12 Dexterity save or be flayed by several lashes from this spell's effects, taking 2d6 Slashing damage. A successful save negates damage by half. Resistances to slashing damage are applicable.