|“||That which does not become part of the one, shall become one with the void.||”|
Unicron is the Chaos Bringer -- a near-unstoppable force of nature. Consumption is the core of Unicron's being, providing the dominant characteristic of this dark, god-like entity. It devours everything in its path, from space trash to whole worlds, fully aware yet completely unrepentant about the dire consequences these actions have on living beings. Unicron exists above and beyond such petty moral concerns, seeking only to absorb all things in order to satiate its unquenchable and inexplicable desire for more power. This insatiable hunger has led the creature known as Unicron across not only whole galaxies, but also entire universes and dimensions as well. Since Unicron's thought processes, not to mention its immense size, put it on a plane of existence far beyond the average lifeform, it often employs agents to prepare the way for itself and deal with any mortal beings that could potentially stand in the way of its goals. These agents are usually super-powerful beings that Unicron has encountered and been somehow impressed by during its travels. Unicron itself was actually staggered and seemingly annihilated by the combined might of the Transformers, but many have become suspicious about whether this force of nature can ever truly be destroyed.
The true origins of Unicron are unknown, but his existence is legend throughout the known universe.
Unicron's original physical body was constructed by the ancient genius known as Primacron at the dawn of the universe. Primacron had hoped that his creation would scour the galaxy clean of life, leaving a blank slate for him to experiment upon. However, Primacron's battle-station was possessed by the even-more-ancient god Unicron, and naturally, Unicron had no desire to be the servant of another. Unicron turned on Primacron, badly wounding him and his assistant, and setting out into the depths of space.
Unicron was the force behind the opening TP of the MUX in 1997. He arrived "early" (compared to some other Transformer continuities), and was defeated by the combination of Autobot and Decepticon forces, with the unwitting assistance of an unknown alien.
Years later, while heading into space to retrieve a sample of the Swarm from a derelict spacecraft being towed into Earth orbit by Omega Supreme, the Decepticon Aries came under attack from the Autobot bounty hunter, Devcon. His attempts to enter the spacecraft were doomed to failure, and Devcon nearly destroyed Aries, sending his body floating off into the vastness of space.
Three days later, he was found by the most unlikely of sources: the head of Unicron, somehow still active in spite of his apparent destruction in 1997. Giving Aries the choice of annihilation or rebirth to serve his will, the engineer nearly opted to be destroyed, rather than be a slave to the Chaos-Bringer’s will. But the thought of not being able to see Discretion again tipped the scales, and Aries agreed.
In that moment, Aries died… and Harbinger arose from the ashes like a dark phoenix.
Harbinger’s transfiguration came as a shock to the Decepticons -- Unicron had been believed destroyed, and now here stood a new herald.
But there was still a hint of Aries within, some of the mannerisms -- it was enough for Discretion to leave with him, and for another Dominicon named Delusion to grab on at the last second.
The trio were captured on the moon by Spec-Tor, an alternate universe Junkion herald of Unicron, and his cohorts in Evil, Inc. It was there that Spec-Tor decided to see if Unicronian energy could be drawn out of others -- and Harbinger was the experiment. It succeeded, and while Spec-Tor put the energy back in afterwards, there was a change -- Aries’s persona managed to reassert himself over Harbinger’s and take full control of his new form.
After a month, Harbinger and Discretion were released, and the Decepticons took them into their own custody. It was at that point that Harbinger (as he continued to call himself) began to show his technical and intellectual expertise, devising a phase-cloak generator that would phase Unicron’s head out of physical reality and, hopefully, render the dark god powerless to act in the universe any longer.
Instead, Unicron altered it even as it triggered, gaining temporary control over time itself. Harbinger was aged mentally by the blast, but with assistance from the Autobots (most notably Dust Devil, who had become a possible future Autobot leader named Stormfront), Harbinger was able to defeat Unicron and destroy his head.
Unicron is a force of nature, however, and his evil energies still linger. With Spec-Tor's isolation and subsequent disappearance, Big-Time has taken over Evil, Inc, and continued Spec-Tor's mission to gather all of Unicron's dissipated energies into the Disco Star.
The MUX Unicron is close to the animated movie Unicron -- evil, powerful, and vast. Since the comics aren't canon on TFU, his involvement with Primus isn't themely. Since season 3 of the cartoon isn't themely either, he was not built by Primacron. Therefore, on the MUX, his origin is unknown and possibly unknowable...
On the MUX, Unicron was responsible for bringing Galvatron here from another dimension in which Megatron was killed, as well as creating Cyclonus, Scourge, and the Sweeps from the remains of an unknown Decepticon patrol unlucky enough to run into him in 1997.
In an alternate universe, Unicron was destroyed by Rodimus Prime in 2006. His head landed on the Planet of Junk, which he took over, creating new heralds and sending them into our universe in preparation for a takeover. Autobots from our world managed to destroy the head, and Wheeljack closed the rift this Unicron created, stranding his heralds and ending the threat of invasion.
When Unicron attacked Cybertron in 2005, Optimus Prime was able to defeat the Chaos God using the Matrix, cementing the Autobots' feeling of invulnerability. Without a leader, Cyclonus and the Sweeps settled on Chaar, where they eke out a meager existence while plotting their revenge on the Destroyer of Unicron.
G.I. Joe World
When Unicron attacked Cybertron in 2005, Megatron forced Autobot prisoner Hot Rod, to open the Matrix that Megatron had ripped out of Optimus Prime's chest. Once Unicron was destroyed, Megatron killed this "Last Autobot," believing then that he had extinguished the final spark of the Autobots forever.