For "failing to perform her wifely duties", Zev was sentenced to become a love slave, a process performed by a machine called the Lusticon. The love-slave transformation process went fine through the first few steps: altering Zev's body to be physically perfect and self-maintaining, changing her hair color to light-blue, and heightening her libido. But before the final step could occur — re-adjusting her mind to make her madly in love with her intended owner — a loose Cluster Lizard interfered with the process. Zev was fused with the cluster lizard, absorbing some of its DNA, from which she gained increased strength and was able to break her restraints. She escaped from the Lusticon and placed the head of a decapitated 790 robot in its path. The robot head (790) received the adjustment instead and immediately fell in love with Zev.
Zev died early on in the second season, in the episode "Terminal". In the next episode, "Lyekka", she was reanimated by Lyekka (combining proteins with another humanoid, to explain her altered appearance) as a present for Stan. The new Zev (called Xev) is more aggressive and has also come to the rescue of her crewmates on multiple occasions.
Although Stan is usually the Captain, both Zev and Xev have held the key to The Lexx at some point during the show's run.
Throughout the series, Zev/Xev's heightened libido is constantly frustrated. She is madly in love with Kai, but he cannot return her feelings because he is dead. 790 worships her, but does not have a body. Stan also frequently comes on to her, but even with her heightened libido, she still finds Stan repulsive. Zev/Xev propositions many of the men she meets throughout the series, but circumstances usually lead to their violent deaths before she can get anywhere with them.
Zev has the ability to transform into a cluster lizard, however this transformation is rare and involuntary. She has also developed the ability to curl her body into a ball-like shape and roll around at a considerable speed like her cluster-lizard "relatives" in season three, and can also make noises like them. In season four she also entered the cluster lizard mating cycle causing her to act strangely for a time. When she encountered a reincarnated Kai on Earth she had a blackout wherein she may have mated with him and then ate him.