The Cluster is a home star system of the Alliance, containing their four primary planets, and termed for their close proximity to each other.
Within their home-system, the collective name for the planets Bone, Fire, Ice, Rock, and the dead-world Remora, is "the Cluster". This describes the relatively close proximity of the four worlds, and it is this proximity, and the imbalance in the resources produced by each world, that has resulted in their history being fraught with war and frequent resource raids.
After the star system containing planets Water and Tek is destroyed, it is the Cluster that the Beast Forces set their sights upon conquering next, quickly establishing a stronghold hidden deep within Remora.
A sixth planet also existed as part of the Cluster, and was used for the purpose of housing the most dangerous criminals of the other worlds. This world was simply known as the Prison Planet, however it ceased to be part of the Cluster after the activation of its Teleport Engine by the escaped prison population.
All that remains within the Cluster of the Prison Planet is a large asteroid belt that may be the shattered fragments of the world after the section containing the prison itself was teleported away, leaving the bulk of the world behind, destabilised and in an unstable orbit.
The presence of the World Engines within the inhabited worlds of the Cluster gives rise to the possibility that the worlds are artificial, which would readily account for their unusually uniform and specialised environments. From this assumption it is possible that the Cluster was in fact entirely engineered by an ancient, advanced race, with intentional disparity between each world's creation of particular resources required for advancing civilisations to survive; forcing them to either act in harmony, or compete for one another's resources.
As elements of the Cluster appear in all episodes of the series, only items of particular significance shall be listed here.
- The four major planets of The Cluster System represents some of the planets of our solar system: Fire = Mercury and Mars, Bone = Venus and Uranus, Rock = Earth and Jupiter and Ice = Neptune.
- Remora is equivalent to Pluto and Eris (proto-planets).
- The first planet to join the Alliance is Ice, then Fire, followed by Bone, and finally Rock. Bone temporarily left the Alliance after abandoning their fleet during the battle of Remora, but after Emperor Femur admitted his guilt for the cowardly acts he committed during the fight with Remora and solved a food shortage, he and his planet were welcomed back into the Alliance. After that, Planet Sand joined the Alliance, and Planet Jungle ultimately allowed itself to be used as a weapon against the Beast, with a single plant from its world evacuating to the Alliance under Femur's care.
- Fire is the only Cluster planet to be devoured by the Beast Planet. Rock was, on several occasions, in danger of being destroyed, and Bone averted at least one doomsday scare.