Kill the Sra'thik Swarmlord at Sra'vess in Townlong Steppes.
While we're here, we should do one more thing. The Sra'thik Swarmlord is responsible for directing the mantid forces from the air. If we leave it alive, it's going to cause trouble for the garrison. So we're not going to leave it alive. Let's take it out, $p.