Planet X (Cybertron)

Once, in the distant past, Planet X was a world to be feared. Existing in a parallel reality, it was home to a race of warriors, thieves, assassins, and techno-marauders, who turned the very planet itself into a colossal weapon that they used to wreak terror and destruction across the face of their universe, obliterating all other worlds and civilizations that stood in their path. This unholy crusade was ultimately Planet X's own undoing, however; when it entered into a war with Gigantion, the Giant Planet, the scientists of Planet X were forced to unleash energies so uncontrollable that they consumed their world, destroying it utterly.

With the destruction of Planet X, what few survivors of the world that remained entered into an alliance with the world-eater Unicron, agreeing to serve him in exchange for a chance at revenge on Gigantion. While the planet itself is no more, "Planet X" remains a phrase of fear uttered only in hushed tones, for now, it serves as a codeword that links these survivors, who have become a secret society whose every action is shrouded in mystery, misdirection and deceit. Nobody knows just how many survivors there are out there in the universe, but it can be assured that wherever one of them appears, tragedy will soon follow in the wake of their passing—a fact proven most visibly by the only two known, named survivors, Sideways and Soundwave.

Cybertron cartoon
Learning that the energy of their world, and indeed, all life in their universe, was slowly dying out, the inhabitants of Planet X reached out to the fringes of space and time, discovering the planet Gigantion in a neighboring dimension. Intending to make it their new home, they pulled it through a space warp into their universe and immediately laid siege to it. Unfortunately for Planet X, Gigantion was one of the worlds chosen by the ancient Cybertronians to be a colony planet, complete with a Cyber Planet Key, the energies of which the Gigantion were able to utilize in order to increase both their size and power, and the size of Gigantion itself, in order to fight back. The war steadily escalated, until Planet X "dropped the big one", and inadvertently destroyed themselves with a weapon they could not control.

Immediately after Planet X met its end, the surviving scholars of the planet pooled their knowledge in a quest to find a means of revenge against Gigantion. Lore of an ancient, planet-devouring being brought them hope, and they split up across the universe in their search for it. It was Soundwave who would end up succeeding in the millennia-long quest, finding and entering into a bargain with the chaos-bringer, Unicron: one million years of servitude in return for the assured destruction of Gigantion. Fellow survivor Sideways later joined him in his pact, even serving as an avatar for Unicron's spark during the war for the Mini-Cons on Earth in 2010.

As misfortune would have it, the Planet X survivors' contract with Unicron reached its end just as Unicron himself was destroyed in 2020. When the Autobots and Decepticons subsequently undertook the quest for the Cyber Planet Keys, Sideways and Soundwave took matters into their own hands, confusing and conspiring with the two factions with the aim of eventually procuring all four keys and using their power to take their vengeance on Gigantion. When the keys were all assembled and Megatron and Starscream began battling for possession of them, Sideways and Soundwave tried making a grab for the keys, but were caught in the reality-rending energies released by the two Decepticons' battle and blasted into another dimension. As it turned out, this was to be a happy ending for the pair, as they discovered an intact version of their home planet in this other dimension, and set up residence there.

Ask Vector Prime
The Planet X of Aurex 802.23 Alpha was originally a peaceful world hailing from Primax 994.0 Gamma. This changed after Jhiaxus and the Cybertronian Empire took over the planet, colonizing and cyberforming it. After the Cybertronian Empire fell, the remnants of its forces, led by Firecrest, fell back to Planet X, cloaking and fortifying it. Due to the constant searching of The Veteran, Planet X and its inhabitants fled their reality entirely and found a small pocket universe which they waged war against, though the inhabitants scorched their reality in favor of being slaves to the Cybertronian Empire. With little energy and life remaining in their current dimension, Planet X again shifted realities and found Gigantion.

However, the Planet X that menaced Aurex 105.08 Alpha was the shattered carcass of Unicron from Primax 886.0 Gamma, which had been inadvertently blasted into Tyran 609.08 Kappa by Rodimus Prime and the Matrix. Unicron hung around the Solar System as an unnoticed "Tenth Planet", but the universe's nature as a binary end-state universe prevented him from fully repairing himself. In an attempt to fix this, his comatose self resurrected many of the Transformers he'd eaten. They dubbed their world Planet X, warped over to Primax 290.0 Zeta, and started conquering the place until the local Autobots used Zodiac energy to drive Unicron's presence out. Half of Planet X went with it, ending up in Aurex 105.08 Alpha to battle Gigalonia, while the other half remained as a paradise world.

Universal stream Viron 704.08 Gamma also had a Planet X. The population of this Planet X was united by a seeming non-singularity version of Unicron, a conqueror and tyrant who used the power of a Cyber Key to merge his consciousness with his planet and proceeding to try to consume the universe before Omega Prime and Fortress Maximus stopped him.

Known Planet X residents

 * Sideways
 * Soundwave
 * Laserbeak
 * Multitudinous Noisemazes Mass Production Type Version
 * Huge quantities of Laserbeak drones

Super INFINITY
In Super INFINITY, Planet X was the home world of Sideways and Soundwave and later the new home planet of the Decepticons and the Predacons. Planet X had the Plasma Energy Chamber and its own Core. It equipped with the planetary engine.

Planet X appeared in Unicron Trilogy. Learning that the energy of their world, upon their arrival in the universe, was slowly dying out, the inhabitants of Planet X reached out to the fringes of space and time, discovering the planet Gigantion in the Milky Way Galaxy. Intending to make it their new home, they pulled it through a space warp into the Andromeda Galaxy and immediately laid siege to it. Unfortunately for Planet X, Gigantion was one of the worlds chosen by the ancient Cybertronians to be a colony planet, complete with a Cyber Planet Key, the energies of which the Gigantion were able to utilize in order to increase both their size and power, and the size of Gigantion itself, in order to fight back. The war steadily escalated, until Planet X "dropped the big one", and inadvertently destroyed themselves with a weapon they could not control (It is revealed that it blasted into another dimension).

Later, the Decepticons teleported Planet X via the space bridge-forming pillars from Sentinel Prime's ship, the Ark II in order to acquire Earth's resources to re-energize Planet X. The planet had been transported into the Sol system, into Earth's orbit, where its gravity wreaked havoc with the planet's natural balance, unleashing an unending torrent of energy created by natural disasters. The energy acquired re-energized Planet X enough to put it out of the danger zone, but the planet was soon knocked out of orbit by a massive energon explosion, and set drifting off through the solar system. Planet X had exited the Sol system, but it arrived at Chaar's solar system. By this time, the Decepticon and the Predacon forces had succeeded in using Planet X as their new home world after being exiled from Cybertron to Chaar by the Autobot and the Maximal forces.

Foreign names

 * Japanese: Planet X (プラネットX Puranetto X)
 * Armenian: X Molorak (X մոլորակ, "Planet X")