Tenacious Plague

Warlock Invocation
Level: Greater, 6th lv.
Components: V, S
Casting Time: 1 standard action
Range: Long (400 ft. + 40 ft./level)
Duration: 1min/lv
Saving Throw: None
Spell Resistance: No

You can summon a swarm as Insect Plague. You add your Cha modifier to the swarms distraction DC. Damage inflicted is treated as Magic for the purpose of Damage Reduction.

Insect Swarm:
You summon a number of swarms of locusts (one per three levels, to a maximum
of six swarms at 18th level). The swarms must be summoned so that each
one is adjacent to at least one other swarm (that is, the swarms must fill one
contiguous area). You may summon the locust swarms so that they share the area of other
creatures. Each swarm attacks any creatures occupying its area. The swarms
are stationary after being summoned, and won’t pursue creatures that flee.

(Complete Arcane, Page 134)