Slicing Shadow

This spell creates a smoky, immobile cloud in which black, whip like whorls of deeper darkness appear and disappear. They have only momentary solidity, yet they slice as if they were unbreakable, razor-sharp ribbons of steel. All creatures who come into contact with a slicing shadow suffer 4d4 points of damage per round of contact, except its caster, who can move and act freely within the cloud without suffering harm. During every round in which they are in contact with the cloud, creatures are allowed a saving throw vs. spell. If it is successful, they take only 2d4 points of damage on that round (additional saving throws must be made for each round).

The caster can choose what volume of area to affect with the spell (up to the maximum) and can end the spell early if desired.