Lexx is a biomechanical insect the size of Manhattan. He was grown on the Cluster, the capital of the 20,000 planets ruled by His Devine Shadow. Lexx was bioengineered with the most powerful weapons of destruction in the Light and Dark Universes. Because Lexx is a living creature, it needs to eat to provide energy to maintain itself and its weapons. Lexx takes commands from the person who holds the key.
Lexx, the most powerful weapon in the Two Universes
The ship was created to put the final boot on the metaphorical neck of the Light Zone by destroying not just the rebels, but the rebel planets. Fortunately for the Light Zone, Stanley Tweedle, Xev, and Kai are in possession of the Lexx and they have no desire to attack the rebels. Lexx belongs to the Divine Order, and His Shadow wants him back.
Lexx taking off
The key to the Lexx is a bioengineered entity that lives in the brain of the holder. Lexx responds to and obeys the person who holds the key. Stanley Tweedle has the key and commands the Lexx. Lexx is about as bright as your average Labrador retriever, he talks, listens, and takes things literally. He's blown up a planet or two in error. Oops.
One of many planets Lexx destroyed