Creeping doom

Creeping doom is a conjuration spell that calls into being a carpet of insects that attacks at your command.

Effect
When cast, creeping doom calls forth a mass of a thousand venomous, biting and stinging spiders, scorpions, beetles, and centipedes in an area of twenty square feet. The swarm attacks anything within the area of effect, but can move up to ten feet every few seconds if no prey is available. Once one of the creatures bites something, it immediately dies.

If the swarm travels more than a hundred feet from the caster, its individual creatures begin to die the further they travel. Otherwise, there are a number of ways to thwart or destroy the creatures forming the swarm; anything that would deter or destroy normal insects is effective against these insects.