The third season of the Transformers animated series continued Unicron's story from where the movie left off, as the planet-eater's deactivated head settled into orbit around Cybertron, a grisly monument to the moons he had destroyed. His head was soon visited by Cyclonus, who accessed the memory bank to discern the fate of Galvatron, who had been hurled from Unicron through space by Rodimus Prime. Some time later (Episode 81: "Ghost in the machine"), the ghost of deceased Decepticon Starscream reactivated Unicron's head and entered into a bargain with him, performing three labors in exchange for the restoration of his body. Starscream (inhabiting and controlling Scourge's body) gathered for Unicron Metroplex's eyes (breaking one and replacing it with one from Trypticon) and Trypticon's transformation cog, and then began connecting his head to Cybertron, which would become Unicron's new body. Starscream demanded that Unicron restore his own body so that he could complete the required connections; but once Unicron had done so, Starscream, somewhat predictably, double-crossed him and refused to finish the job. Unicron's head was subsequently blown off into space by an explosion instigated by the Autobots.
Later, when searching for a new supply of anti-electrons, the Decepticons ventured to Unicron's head, where Cyclonus and Scourge accidentally awoke the slumbering demi-god. At the same time, Grimlock - who had gained super-intelligence through an infusion of anti-electrons - had constructed from pieces of Unicron's head the Technobots, and one of their number, Strafe, severed enough of Unicron's neural connections to shut him back down.
Although Unicron himself did not appear again, his origin in the animated series was later revealed. Unicron was created near the beginning of the universe by the diminutive genius known as Primacron, who intended for him to devour all life in the universe, leaving a blank slate that Primacron could use as he saw fit. However, Unicron turned upon Primacron, deciding that he would rule the universe and subsequently setting out to achieve that goal.
Unicron's head was seen one last time as Primacron's new creation had crippled Cybertron. This time the head looked very old and almost stone-like, underlining that Unicron was finally dead.
In the series, Unicron was voiced by Roger C. Carmel.
He and Primus clashed many times, the force of their battles wiping out the very life Primus had been created to protect. To stop this physical destruction, Primus shifted the battle to the astral plane, where he fared little better, forcing himself into what seemed to be a sacrifice play - in shifting the battle back to the physical universe without time to properly generate their energy forms, Primus entrapped both himself and Unicron in two barren asteroids. But this was not the end of Unicron - over the eons, he learned to psionically shape his asteroid, and transformed it into a metallic planet, and then again into a gargantuan robot. Primus, fearing that to follow suit by forming himself in a similar manner would simply pick up the conflict where it had left off, sought an alternative way to defend the universe against the threat of Unicron by turning his asteroid into the planet Cybertron; a planet that he populated with robotic beings that, like Unicron, could alter their forms. And thus were born the Transformers.
In the comics' version of post-movie events, Unicron's head did not enter Cybertron's orbit, and instead crash-landed on the Planet of Junk. Still active, Unicron used his vast mental powers to enslave the minds of the Junkion natives, who set about rebuilding his body. Cyclonus, Scourge and the bounty hunter, Death's Head, also fell prey to him, and he used them to exacerbate the stalemated war on Cybertron to keep the Autobots busy, so that they would not learn of his impending resurrection. When Death's Head fought back against Unicron's mental control, however, Unicron rewarded his temerity by revealing the comic book version of his origin. Death's Head then aided Rodimus Prime, projecting his mind into Unicron's where they battle, until Unicron's head was destroyed by explosives, and his essence was sealed within the Matrix. Rodimus and several other future Autobots subsequently travelled back in time to 1989 and participated in the "Time Wars," but when they attempted to return to their own time afterward, they discovered that disruptions to the timestream had erased their future, and replaced it with one where the Decepticons ruled Cybertron. In this dark future, Unicron's essence emerged from the Matrix and briefly took over Rodimus Prime, before he was thwarted by the removal of the Matrix from Rodimus's body. In 2010, however, Unicron attempted this again and succeeded, controlling Rodimus's body and reshaping it into his own image, before being defeated by Rodimus's own force of will.
A battle between the Autobot Classic Pretenders and the Decepticons' Mayhem Attack Squad at the centre of Cybertron had the unfortunate side effect of waking the slumbering Primus, who was struck by a stray laser blast and awoke with a scream. Although he immediately sank back into slumber, Primus's scream echoed throughout the universe, to the fringes of known space where Unicron heard it. Now aware of his old enemy's location, Unicron immediately headed towards Cybertron, but, seeking a herald to sow chaos in his name ahead of his coming, used his formidable powers to send three agents - Hook, Line and Sinker, forward in time to an alternate future version of 2009. In this timeline, Unicron had succeeded in consuming Cybertron in the year 2005, and Galvatron and the Decepticons ruled Earth. This timeline's version of Galvatron was pulled back to 1990 by Hook, Line and Sinker and press-ganged into Unicron's service, but, like his predecessors, turned on his master by forcing Emirate Xaaron to awaken Primus in hopes of destroying Unicron. Primus possessed Xaaron's form and attempted to hold off Unicron, but he was weak, and his attack was a ruse, leading to his own destruction, which in turn (along with a direct attack by Galvatron) succeeded in galvanising the Autobots and Decepticons to attack Unicron together. Ultimately, they did little damage, and many Transformers died (including Waverider) before Optimus Prime was able to use the Matrix to destroy Unicron, exploding his body from within.
In contrast to his major roles in the Marvel comics, the cancellation of the Dreamwave Transformers comics meant that Unicron would play a much lesser role in events. His presence was first hinted at in the second "War Within" arc, where the Fallen enlisted the Chaos Trinity (Bludgeon, Bugly and Mindwipe) to capture a number of Transformers (Grimlock, Blitzwing, Jetfire and Hot Spot) for an arcane ritual to summon the Fallen's Master. It failed, due to a combined strike by Prowl's Autobots and Shockwave's Decepticons, with the Fallen being killed by Primus himself.
He would make his first mainstream appearance in volume 3, issue 1 of the main Generation One series, seemingly summoned by Shockwave at the end of the previous volume. Here it is revealed that he had dispatched Scourge at the head of a huge armada of Sweeps to search the galaxy for Cybertron. Scourge located it, but was shot in the back and deactivated by Shockwave, who used analysis of his body to create the Triple Changers. Unicron then destroyed Lithone, before beginning to journey to Earth. Dreamwave went bankrupt and the next issue was never released. Writer Chris Sarracini has indicated that he would have followed through on the Unicron storyline, and also would have had the Dreamwave version of Cyclonus rescue Scourge from US government study.
Apparently banished from his world thousands of years ago, Unicron travelled the galaxy, devouring planets to quench his hunger and taking their populations as slaves to maintain his inner body works. However, when attacking the seemingly primitive and defenseless Earth, Unicron ran into trouble. A strange set of non-human creatures opposed Unicron, threatening to attack him with a metal devouring organic spore. Before the two sides could annihilate each other, an agreement was reached favouring both parties. The creatures would go into hiding, allowing humanity to develop. Then, when they had reached a sufficient technological level to serve as slaves for Unicron's inner workings, the creatures would call Unicron. He would destroy humanity and they would inherit the human-free world he left behind. Thousands of years later the pact would be kept and the creatures, now calling themselves Cobra-La, would summon Unicron via a beacon. Attacking a pirate vessel on the outskirts of a solar system, Unicron then journeyed to Earth. Hailed as the "Doom Star" by terrified humans, Unicron transformed to robot mode and prepared to destroy humanity. However, he was thwarted when Cosmos and Flint travelled through his mouth into his body bearing the metal-eating spores of Cobra-La. Despite the best efforts of his "anti-bodies" (the Beastformers), they delivered the spores directly to his brain. Although he was not shown to be destroyed, he was last seen entering convulsions, indicating he would no longer be a threat. It was later mentioned his body was floating around Earth.
In this continuity, Unicron is thought of as the Transformers' equivalent of the "boogeyman". The revelation that Unicron had been banished from his home planet indicates a different origin from ones used for previous incarnations of Unicron.
As with his original incarnation, there was a failed attempt to make Unicron into a toy for the Beast Wars Neo line, and although regarded as quite impressive, the prototype - which, notably, does not resemble Unicron from the Beast Wars Neo series at all - did not make it into the production.
Although the end of Universe would preclude a proper conclusion, the Cybertron Club Comic would offer a resolution. When Optimus Prime would be called to another dimension to fight Unicron's heralds, he would reflect back on the final battle between Primus' forces and Unicron's army - where Unicron suddenly disappeared, his existence ended by the black hole created by his defeat in Transformers: Energon.
This incarnation of Unicron was never shown to physically consume planets in the same manner as his G1 predecessor, only to blast and absorb the remains. However, during his battle with Optimus Supreme, who had grown to Unicron's size, Unicron demonstrates that he had enough power to simply destroy a planet completely without consuming it. However, several references were made to consumption, so he may indeed perform the action (Note: In one of the mini-comic books packed in with the later Armada toys, Unicron is indeed illustrated literally eating an asteroid or moon whole). This Unicron was voiced by Mark Acheson in the US, and by Katsumi Chō in Japan.
The subsequent awakening of the Mini-Cons once again increased the pace of the war, and to hasten the proceeding, Unicron created another being from his own body, Sideways, to serve as his agent for the purpose of constantly manipulating the events on Earth to keep the balance of power forever shifting, the ferocity of both sides constantly increasing. At the culmination of his plan, the Decepticons came into possession of all three Mini-Con weapons - the Star Saber, the Skyboom shield and the Requiem Blaster - which Sideways and Thrust then stole and used to reactivate Unicron. Shedding his lunar skin, Unicron transformed to robot mode and turned on Cybertron as the combined Autobot/Decepticon armada attempted in vain to stop him. Optimus Prime and Megatron (now Galvatron) entered his body with the human children, and Unicron addressed them through Sideways's form, absorbing all but Optimus into his collective consciousness and bringing the Mini-Cons back under his control. However, from within Unicron's mind, Rad was able to use his connection to High Wire to restore the Mini-Cons' individual minds, freeing the weapons and deactivating Unicron. With the danger apparently over, Galvatron challenged Prime to a final battle, but the hatred between the foes stirred Unicron to life again, and Galvatron realised that to break the circle, he had to sacrifice himself. Plunging himself into Unicron's maw, Galvatron ended the hatred, and in a mighty flash, Unicron vanished without a trace.
Unicron's body, damaged once more, lay in the dark reaches near the fissure, and the Decepticons began to raid Alpha-Q's new planets for the Energon necessary to revive Unicron again. This time, they succeeded, and Megatron directed Unicron's body to retrieve his head, extinguishing the Energon Sun and killing Alpha-Q in the process. But the power of Unicron proved too much for Megatron to control, as Unicron began to take over Megatron's body. In the ensuing battle Unicron's body was successfully destroyed by super-powered Optimus Supreme with help of some of the other powered Autobots. Unicron's body was destroyed - but unbeknownst to anyone, he lived on in two forms: his minuscule Spark, and his consciousness, which lay buried in Megatron's mind. With quiet, subconscious nudgings, Unicron led Megatron to a massive reservoir of "Super Energon" beneath Cybertron's surface, which transformed him into Galvatron upon his first exposure. After a series of failed battles, Galvatron proceeded to expose himself to the Super Energon once again, and this time grew to a gigantic height. Unicron seized control of his body again for a new vessel and set out to rejoin with his Spark, but a Primus-empowered Optimus Supreme engaged him in battle once more, and drew all of Unicron's consciousness out of Galvatron and sealed it within his own Spark. Enraged, Galvatron prepared to destroy Unicron's Spark, but it merged with him, enlarging him again, leading to another battle with Optimus Supreme, this time bolstered by the combined energy of all his troops' Sparks. Meanwhile, Primus merged with the Super Energon, creating a foundling sun which arrived at the site of the battle. Taking control of his body for a brief moment, Galvatron once again sacrificed himself in order to stop Unicron, plunging himself into the infant sun, which ignited and gave new life to Alpha-Q's worlds.
However, the Japanese equivalent, Galaxy Force, made several scattered references to Unicron, as the Japanese producers for the series decided not to have Galaxy Force follow on from the events of Micron Lengend (the Japanese equivalent of Armada) and Super Link (the Japanese equivalent of Energon).
The toy of Unicron in the Cybertron series is the size of a deluxe class Transformer toy and transforms into a Cybertronian tank instead of a planet. This portrayal of Unicron is consistent with his appearance in the Cybertron strip in the Hasbro Club Collector's comic where he is portrayed at around the same size as his foes Sentinel Maximus and Omega Prime.
His coming in the Armada comic universe was first foreshadowed when he pulled Optimus Prime into a parallel dimension where Cybertron had been devastated. In return, Unicron sent something into our universe - the near dead Optimus Prime of the parallel universe, who warned them of Unicron's coming before dying. Subsequently Unicron sent his Heralds - alternate of the Generation 1 versions of Galvatron, Scourge, Thunderwing, Dirge and Bludgeon - ahead to destroy those who could oppose him (including Megatron) and capture the Mini-Con Matrix. Galvatron was eventually killed by Megatron using the Star Saber, and the other Heralds were eventually destroyed in their captured Decepticon base by an explosion engineered by Jetfire. Unaware of his Heralds' failure, Unicron now threatened to destroy Prime, but the Mini-Cons and Jetfire managed to rescue him, with the power of the Mini-Con Matrix upgrading them and combining them into their Powerlinked mode. They held off Unicron long enough to escape back to their universe. Unicron then came to the Armada universe himself, where he was attacked by a combined force of Autobots and Decepticons. They distracted him long enough for the Mini-Cons to access the power of the Mini-Con Matrix and destroy the Chaos-Bringer. Here Unicron never even transformed to robot mode.
Unicron survived, but his body was crippled and he no longer had the power to transform or even move. He was forced to employ servants to do his bidding: Alpha Q and the Terrorcons, who were disgruntled former Decepticons upgraded by Unicron in return for harvesting enough Energon to repower him. While they attacked Earth, a rich source of Energon, Unicron sent his four Horsemen - Rhinox, Airazor, Terrorsaur and Cheetor, absorbed by Unicron in the previous battle - against Cybertron, devastating much of it before being stopped by Optimus Prime. Many of the latter Energon stories were set inside Unicron himself as Megatron, whose Spark had also survived the previous battle, attempted to convince Prime to resurrect him in a new body, with the planet eater seemingly unaware of their actions.
Alpha Q showed signs of rebelling against Unicron, and Prime prepared to fight back from inside Unicron. However, the series was canceled before these plot threads could come to fruition. Writer Simon Furman revealed that a future storyline of the Energon comic would have included another attack by Unicron, had the series continued.
A new Unicron figure was released at the end of the Cybertron toy line as a Deluxe-class figure with a tank-like alternate mode. Although the character did not in Transformers; Cybertron or its Japanese equivalent Transformers: Galaxy Force, the Hasbro Club comic served to introduce this new version of the Chaos-Bringer. In this story, the black hole contains Unicron's essence and also links him simultaneously to all Cybertrons across the Multiverse giving him the potential to wipe out Primus in one fell swoop. This course is currently being held at bay by Transformers from across the Multiverse, usually consisting of characters derived from Convention and Club exclusives as well as Cybertron figures that play no role in the television series. In one issue, Soundwave was dispatched to Cybertron after Ramjet and Nemesis Prime's failure. He tosses the Dead Matrix into the black hole, releasing Unicron's spark which quickly overtakes a nearby world, converting its inhabitants into savage maniacs. With the destruction of the planet his body is reborn as a normal sized Transformer.
When Unicron eventually attacked Cybertron in the midst of the chaos caused by a Mini-Con civil war, Sentinel Maximus and Omega Prime fought him off with the help of their allies. In the end Unicron was driven off badly wounded again, this time by Primus himself.
This concept began with the release of a series of Transformers: Armada trading cards by Fleer. The biography printed on Unicron's card presented him to be one of two heralds created by the Allspark to explore the newly-birthed universe. Inspired by his Marvel Comics origin, the other herald was Primus, and the brothers set about this task, until they came upon a region of space teeming with pure Energon. Unicron wanted this power for himself, and cut Primus down before he could report it to the Allspark, casting his brother's body into the orbit of a nearby star. And so Unicron went on to become the engine of destruction that menaced the universe in recent years.
Not long after this, the publication of Transformers: The Ultimate Guide by Dorling Kindersley cemented this notion. Writer Simon Furman incorporated the various aspects of the Dreamwave Comics story, some elements of the Fleer storyline and his original Marvel Comics origin to create what is now essentially the "definitive" origin for Unicron. In this version of events, Unicron and Primus were again twin heralds, giant metal planetoids created by the "One", who were sent to explore the universe. But Unicron was an imperfect being and turned to evil, adapting his form to transform into a giant robot. To battle him, The One gave Primus this power also, but Primus opted to remain in planet mode, and passed the Transforming abilities on to thirteen robots that he created from himself; the first Transformers. One of the thirteen turned on Primus and sided with Unicron, however, and the war culminated in a battle that saw Unicron and this traitor, the "Fallen," sucked through a black hole into another universe.
This new origin is part of the G1 timeline laid down by the Ultimate Guide, which is apparently being taken as the "official" G1 timeline for future projects that require it. This means that canonically, there is only one Unicron who has travelled from universe to universe across all the assorted Transformers continuities. This interpretation of the character is evidenced by the parallel universe spanning Transformers: Universe toyline and convention-exclusive comic books — in which the singular Unicron captured Transformers from various alternate realities and pitted them against each other, feeding off the energies released — and the Transformers: Cybertron comic strip in the Transformers Collectors' Club fan magazine, which depicts Unicron's actions in the various realities in a chronological order and claims that Cybertron is the stable heart of the Multiverse.
The idea of a singular Unicron and Primus remains the official take on the subject, despite any contradictions in other official Transformers fiction.
The comic version of Unicron may be far larger. In the first issue of Marvel Comics Generation One Transformers comic, Cybertron is said to be around the size of Saturn (which has a diameter of roughly 120,000 km at the equator). As Unicron's planet mode is seen to be as large as Cybertron (if not larger) in the comics, this would suggest a diameter of 120,000+ km. The Dreamwave equivalent of Unicron may be the same size, as the Cybertron of the Dreamwave universe was also said to be the size of Saturn.