Summon swarm

Summon swarm was a conjuration spell that conjured a swarm of small crawling or flying creatures.

Effect
When cast, summon swarm caused a swarm of tiny creatures to cover an area, attacking any other creature they encountered. Spellcasting or concentrating on spells within the swarm is impossible. The caster has no choice as to what type of creature he summons; typical swarms include rats, bats, poisonous spiders, centipedes, and flying beetles.

The swarm cannot be fought effectively with weapons, but fire and damaging area effects can force it to disperse. Certain area or effect spells, such as gust of wind and stinking cloud, disperse a swarm immediately if appropriate to the swarm summoned. (For example, only fliers are affected by a gust of wind.)

The swarm is stationary once summoned, not leaving the original area. A druid caster, however, can direct the swarm to move up to thirty feet every few seconds (or ninety feet if she has summoned bats or beetles).

Components
It needed verbal and somatic components, a divine focus for divine casters, and a square of red cloth as a material component for arcane casters.

History
The spell was attributed to Netherese arcanist Jarm in  and was originally called Jarm's summon swarm.

Around the 13 century DR, a pirate-mage by the name of Respitil sailed the Sea of Fallen Stars and was known to cast the summon swarm spell to have biting, stinging insects devour their captives that were bound to the mainmast.