Cluster Lizards are vicious creatures encountered in the Light Zone. They resemble large worms with multi-segmented mouths filled with rows of teeth, and an extremely tough armoured carapace. Their exact planet of origin is uncertain, however they presumably originate from an extremely warm climate, as they are highly resistant to warm temperatures. Considering their name as Cluster Lizards it is possible they do originate from the Cluster in a warmer area of the planet, though it is unknown if the planet ever possessed different areas or had a single consistent climate.
They are extremely dangerous carnivorous predators with an appetite for living creatures and a particular fondness for brains. They are capable of moving at high speed by rolling into a "wheel" by bending backwards to curl their mouth towards the tip of their tail. A fully adult Cluster Lizard stands well above human height even with a large segment of their tail still on the ground.
The most dramatic appearance of cluster lizards is in Lexx 1.1 "I Worship His Shadow", when a group of cluster lizards are caged in a large arena on the Cluster, their purpose being to devour Thodin during a public execution for heresy. Due to his escape attempt however the cluster lizards are let loose in public areas of the arena where they proceed to devour almost everything in sight.
During the events on the cluster, one of the lizards rolls into the area where Zev of B3K is being transformed into a Love Slave. During the process the Lusticon severs the head of the lizard, causing its DNA to be combined with Zev's, resulting in her love slave transformation being terminated early (leaving the helpless 790 to gain the love slave mentality), and leaving Zev a hybrid of mostly human but part cluster lizard. As a result of this transformation Zev is able to screech like a cluster lizard, roll around (still in human form), or even transform into a cluster lizard for brief periods.
In Lexx 1.4 "Giga Shadow", Kai discovers a unhatched cluster lizard egg in the cryo-chamber of the the Lexx, which hatches and believes him to be its mother. The brave little lizard is named Squish by Zev who immediately dislikes it, though it goes on to ultimately destroy the Giga Shadow by eating into its brain.
It is revealed in Lexx 4.9 "Fluff Daddy" that the cluster lizard female has a seven year oestrus period, during which she will become extremely violent and territorial, devouring large meals before finding a suitable mate and ultimately devouring him as well, unfortunately in Xev's case this results in her devouring the entire audience, and finally the star of a live drama performance by the living version of Kai on Earth. It can be assumed from this behaviour that cluster lizards are likely birthed in large groups, as the males are unlikely to enjoy especially long lives.