In the late 2250s, the Qul qemwI' was under the command of Captain Kavau, with Kintazh, son of Gorkon as his weapons officer. The ship and crew were tasked with testing theragen, a nerve gas, by members of the Klingon High Council. Unfortunately, one of the tests backfired, killing three quarters of the crew with the remainder dying uncomfortably slowly.
The use of theragen was officially disavowed following this disaster. Kavau and the crew were branded renegades and criminals, and Chancellor Sturka sent General Gorkon to execute the survivors and destroy the Qul qemwI'. (VAN novella: The Ruins of Noble Men)