This invocation summons masses of biting and stinging insects. One swarm is summoned for every three class levels. A swarm has a +4 base attack bonus (with an additional to hit bonus based on the caster's Charisma x 2) and deals 2d6 points of magical damage when it hits. A swarm dissipates after three rounds. Tenacious plague does not stack with itself - if the warlock uses this invocation while swarms still exist, the current swarms will be replaced with the new swarms.