Omega tribble
Omega tribble was the name given by the Klingon scientist Dr. K'ruvang to the mutated species of tribble that his experimentation accidentally created.
Biology
Created by Dr. K'ruvang's experiments on slowing tribble breeding down with genetic engineering, omega tribbles were even more voracious than usual, and had teeth. Some of the tribbles were around half the height of an adult Human, and at least one was several meters tall.
Omega tribbles were unaffected by phaser and Klingon disruptor fire, even at the kill setting. (PRO: "A Tribble Called Quest")
History
Several years before 2384, Dr. K'ruvang was sent by Klingon Chancellor Martok to find a way to defeat the ancient Klingon blood enemy, the tribbles. He landed his Bird-of-Prey on an Class M planet and worked out of it as a laboratory, focusing on genetic manipulation and hormonal retroviruses. After many years, he found a weakness in the tribbles' DNA, but his experiments went wrong and the tribbles on the planet became stronger, being dubbed omega tribbles by the doctor. Having lost his honor, he was unable to leave the planet until he could defeat his enemy.
In 2384, the USS Protostar landed on the planet seeking the bosonite needed to build a new proto-core for the ship. By this time, the planet was a barren wasteland, everything having been devoured by the tribbles. The crew managed to escape from a wave of attacking tribbles, but Zero broke their leg in the process and beamed back to the Protostar with Jankom Pog for medical treatment.
After meeting K'ruvang, Rok-Tahk -- who had done her Starfleet Academy admissions thesis on tribbles -- was able to help the scientist create a retrovirus to reduce the tribbles' reproduction and their size. However, in the process, Rok accidentally created a Brikar-tribble hybrid named Bribble. Rok's retrovirus was infused into replicated quadrotriticale grain which Rok, K'ruvang and Murf spread outside of the omega tribble nest while Dal R'El and Gwyn rappelled in from the Klingon ship to set up pattern enhancers around the large bosonite deposit in the middle of the nest. The tribbles were drawn out of their nest and consumed the grain, but were seemingly unaffected by the retrovirus, quickly returning to their nest before Dal and Gwyn could escape. As the tribbles surrounded the Klingon scientist and Starfleet crew, Bribble was able to communicate with the creatures and get them to back off.
Dr. K'ruvang later contacted Rok to reveal that the retrovirus had been successful and had simply needed time to work. With the Klingons' ancient blood enemy defeated, K'ruvang's honor was restored and he was able to return home, leaving the greatly reduced and slowed down omega tribbles behind on the planet. (PRO: "A Tribble Called Quest")