The spell was created as an experiment by Project Deathwatch to summon beings from the Plane of Shadow, but had unexpected results. Instead of undead shadows, wisps of cobweb-like smoke were summoned. These wisps blow in seemingly random directions within the sphere of effect.

Anyone caught in the area of effect must make a Reflex save (DC 17) to avoid the wisps’ touch each round they stay within the sphere. Those that fail take 1d10 points of damage and are temporarily drained of 1d4 points of strength. The sphere can be moved as a free action by the caster at a rate of 10 feet per round. 

A protection from evil spell successfully protects against shadow-wisps, perhaps indicating that the wisps are actually creatures of some sort. The material component for this spell is the essence of a shadow.