Primus is Unicron's sibling, and the creator god of the Transformers. His body is the planet Cybertron, and the mega-computer Vector Sigma serves as his internal mainframe. Though he rarely meddles in the affairs of his creations, he has gifted a portion of his life force within the Matrix, which determines the leader of the Autobots. Prophecies of a war to come were written down in his holy covenant as well. The spark of each Transformer is a small piece of Primus' essence, and together they form his life force, the Allspark.
|“||Until all are one!||”|
—Primus to his children, "Trap"
In the beginning
Before the dawn of time, Order and Chaos existed within an extra dimensional entity known as The One. To explore the fledgling universe, he created the astral being known as Unicron, and then subdivided him, creating his twin, Primus. Both brothers were multiverse singularities, unique in all realities, but whereas Unicron could only exist in one dimension at a time, moving between them at will, Primus existed simultaneously in all realities at once. It is suggested, in fact, that the two brothers embody the basic concepts of reality - good and evil, order and chaos - and that their continued existence is necessary for the stability of the multiverse.
As Unicron and Primus went about their appointed task, venturing through the cosmos, it became apparent to Primus that Unicron was a corrupt being, and he took it upon himself to stop the threat posed to all of existence by his sibling. In combat, Primus was no match for Unicron. In cunning, however, he proved himself to his brother's superior when he shifted their battle to the astral plane, and then back to the physical world once more, only to have both their essences manifest within metallic planetoids, leaving them both trapped. It was with this act of sacrifice that Primus hoped to contain Unicron's evil forever. Unfortunately for him, over time, Unicron learned to sonically shape his prison into a giant metallic planet, and Primus followed suit, becoming the mechanical world of Cybertron. When Unicron then learned to transform his planetary form even further, into a gigantic robot form, Primus adapted the idea to suit his own ends - rather than transforming his own body, he would create small beings that would be able to change their shape, like Unicron. After performing a "test run" on the moon of Protos, where he successfully created twelve transforming robotic beings, he birthed from his own body a group of thirteen robots that possessed the ability to change shape, like Unicron. These were the 13 original Transformers, each one infused with a fragment of Primus' life essence known as a spark.
The Thirteen were Primus' soldiers in his war with Unicron, which came to its seeming end during a climactic battle in which one of the Thirteen, who would forever be known as The Fallen, betrayed Primus and became an acolyte of Unicron. The battle ended when the Fallen and Unicron were sucked into a black hole and disappeared from reality. With Unicron gone for now, Primus entered an eons-long slumber, his self-imposed sleep preventing Unicron from detecting him through the mental link the brothers shared. The Transformer race grew, and Primus fell into the realm of legend, with a portion of his power, the Matrix of Leadership, handed down through the generations, serving as the Transformers' ever-present link to their creator.
Evolution of the Primus/Unicron myth
The Primus/Unicron backstory has evolved and been rewritten a good number of times since it first originated in the Marvel Comics series. The version recounted above is the current iteration, which has slowly solidified across a wide swath of media (beginning around the time of Armada). Before the Primus/Unicron mythos reached its present form it went through several distinct versions in the Marvel G1 comics and elsewhere.
The first time we ever heard the Primus/Unicron backstory was in the UK comic continuity, from Unicron himself, in the story Legacy of Unicron, when he recounted it to Death's Head. Per Unicron's telling of events, he was a primal force of evil at the dawn of the universe, who led a legion of Dark Armies against his mortal foe, Primus, Lord of the Light Gods (note the plural). Events proceeded to play out basically as described above, though the role of the Light Gods and Dark Armies would diminish with each subsequent retelling of the story, until the current version, in which Primus and Unicron are alone, and have a unique origin. (Only one of the other gods was ever named - the Chronarchitect. How exactly he factors into the current iteration of the myth is unknown.)
The Keeper's story
The second time the story was told was in the US book by the Keeper, an ancient mechanoid who guarded Primus' head at the center of Cybertron. This telling is effectively the same as the previous UK story, but mentions that their battle was towards the end of the era of gods, that Primus and Unicron were the last of their respective pantheons, and Primus had to defeat Unicron before he could take his place with the other gods in the "Omniversal Matrix".
The third time the story was told was also in the US Marvel series, this time by Primus, when he gathered all his children together to prepare for Unicron's coming. It was with this telling that we learned that Unicron predated the current universe, and had destroyed the previous universe which existed before the current one. He had slept peacefully, alone in the void of uncreation that remained, until fragments of the old universe that he had overlooked reacted, causing the Big Bang and birthing the current universe. The "sentient core" of this new universe recognized the threat that Unicron posed, and so created Primus to counter his evil and be guardian of the new creation.
Fleer and DK
The first modern retelling of the origins of Primus and Unicron did not come from G1-oriented media, but from a set of Armada trading cards released by Fleer. It was the back story printed on Unicron's card which introduced the concept of the two being brothers created to explore the new universe by an extra dimensional entity, here named the "Allspark."
This was subsequently expanded on and combined with aspects of the various Marvel Comics stories in Transformers: The Ultimate Guide, published by Dorling Kindersley and written by Simon Furman, who had written all three prior telling in the first place. Here, the entity Fleer had called the "Allspark" was redubbed "The One," and the modern iteration of the myth detailed above was firmly established, and went on to form the backbone of subsequent fiction such as Universe and Fun Publications' Cybertron comics.
It was also at this point that it was established that Primus could transform from Cybertron into a robot mode like Unicron, but preferred not to, choosing to remain connected to the universe on a planetary level.
Marvel Comics continuity
Eventually, millions of years later, in one version of Generation One continuity, Grimlock, Jazz, and Bumblebee found themselves transported to the center of Cybertron, where they discovered the sleeping form of Primus and were told the tale of his and the Transformers' origins by the Keeper. Subsequently, Bludgeon's Pretenders attacked, and during the battle, a laser blast ricocheted off Grimlock and struck the essence of the sleeping Primus, causing a multiverse-shaking "Primal Scream" that woke Unicron and alerted him to Primus' location. Primus himself immediately slipped back into his sleep, but it was too late.
Unicron dispatched a group of heralds to attack Cybertron and pave the way for his coming, including a Galvatron plucked from an alternate future. Galvatron, however, was not content to serve under Unicron, and instead captured Autobot leader Emirate Xaaron, forcing him to fully awaken Primus, who possessed Xaaron's body and summoned Transformers from all across the universe back to Cybertron. Primus intended for all his children to battle Unicron together, but when the planet-eater arrived, sheer terror prevented them from carrying out his desire. Primus instead made a stand himself, attempting to dupe Unicron into believing he still retained his full power, but Unicron saw through the deception, and destroyed Xaaron's body. Optimus Prime subsequently used the Matrix, the full measure of Primus' power, to destroy Unicron. His body in this universe obliterated, Unicron moved on to another dimension, to ravage other worlds, and make further attempts on Cybertrons throughout the multiverse.
(Note: As originally written, it is quite clear that the story intends for Primus to have died after his battle with Unicron. As the current retcon makes it clear that this cannot possibly be, one must assume that Prime was wrong in his analysis that Primus had died. Notably, even in the original comics themselves, the Matrix - the life-force of Primus - is shown to still exist and is functioning fine in the G2 Marvel Comics series that follows his supposed death.)
The Transformers cartoon continuity
Primus did not exist in the Generation One cartoon as it was originally written. There, Cybertron's oldest revealed status was as a factory world of the Quintessons who invented the Transformers, and Unicron was created by the ancient genius Primacron. The animated continuity is, then, easily the fiction that is least compatible with the subsequent retcon that establishes Primus as a multiverse singularity and part of all Transformers universes, although Wreckers #3 did attempt to retcon the Primus mythology into the Quintesson-creation backstory of the original cartoon.
Beast Wars/Beast Machines
In addition to its occasional invocation in prayer or in righteous anger by the Beast Warriors, Primus' name was also lent to a set of prophetical datatrax, known as the Covenant of Primus. From this document, the Megatron of this era took his name (as did, presumably, the original Megatron), and the scriptures foretold the events which completed the Beast Wars.
After the Beast Wars, Megatron intended to incorporate Primus' essence, the Allspark, into his own being and become godlike by stealing every Spark of every Transformer on Cybertron. Ultimately, this was merely one step of the Oracle's plan to reformat Cybertron into a technorganic paradise. After Megatron and Optimus Primal were plunged into the planet's core, the planet was reborn and the abducted Sparks were returned to new technorganic bodies.
Following the recreation of Cybertron as a technorganic world, Unicron began gathering Transformers from across the multiverse, forcing them to fight and harvesting the Sparks of the losers to restore his power. With each spark devoured, Primus was weakened, and so, communing with Autobot elder Alpha Trion, called back from the Allspark the now-legendary Maximal commander and Cybertron's savior, Optimus Primal, to rescue the possessed, battling captives from the Pit of Unicron -- and to lead a team of multiverse warriors to put a stop to his soul-stealing scheme before it could cause the Allspark to collapse.
Primus allowed Optimus Primal to choose any Transformer who ever existed -- living or dead -- for his army. This required considerable amounts of Primus' power, so Primal was told to choose sparingly. Primal chose his departed former troops Rhinox and Depth Charge. Ultimately, however, Unicron's defeat came not as a result of their efforts, but as a consequence of another battle, happening in another corner of the Transformers multiverse.
In the Unicron Trilogy universe, Primus was introduced as the living energy core of Cybertron, as well as the originator of the precious and ancient fuel, energon. Transformers of this universe believed the stories of Unicron, Primus, and Omega Supreme to be only myth and legend until the existence of Unicron was revealed in the "Unicron Battles" of 2010. With Cybertron left in a disastrous state after the chaos-bringer's attack, large amounts of Energon were required to repair the planet, and to search for and acquire the mineral, the united Autobot-Decepticon forces entered into an alliance with the Earth Federated Government.
Primus entered into the equation when the project's head scientist, Dr. Brian Jones, brought his son, Kicker, to Cybertron. Terrified of the giant robots surrounding him, Kicker fled, only to find himself tumbling through tunnels into a hidden chamber deep beneath Cybertron's surface. Primus awoke and saved Kicker from what would have been a fatal fall, and for his own reasons, imbued the child with a special gift - the ability to detect energon throughout the universe. He also told Kicker that that he found the boy's species interesting and is curious about them. Optimus Prime subsequently discovered Kicker in Primus' chamber, and the god chose to work with the Transformers quite directly, imbuing them with the "Spark of Combination," which would allow the Autobots to combine and increase their powers. Primus went on to advise Optimus Prime on his actions in order to prepare for the future, including the Terrorcon invasion, the return of Megatron, and the next battle with Unicron; although vague at times, he would offer just enough information to allow his children to survive the threats they faced. Primus was often very weak due to the damage done to the planet's surface, and spent most of his time in a mode of stasis to preserve his energy and keep Cybertron's energy grid online.
When Megatron succeeded in reanimating Unicron, most of the Autobot army was critically wounded in the ensuing battle. This prompted the sleeping Primus to awaken and infuse their armor with his power, upgrading them into new forms, and allowing Optimus Prime and Omega Supreme to combine into a gigantic form and defeat Unicron.Unicron's spark survived, however, and Primus sought to contain it by trapping it at the heart of a new sun that he created from a reservoir of "super energon" hidden within Cybertron.
Primus' plan to contain Unicron's essence in the center of the sun failed when the star collapsed into a massive black hole which threatened not only Cybertron and the universe, but the entire multiverse itself. His energy drained to the point that he had once again been rendered dormant, Primus could now only be awakened and restored to full power by the four ancient Cyber Planet Keys, lost to the far reaches of the galaxy in a failed space bridge experiment eons ago. The magnitude of the threat posed to the multiverse was enough to summon Vector Prime - one of the original thirteen Transformers, who had been following Unicron through the multiverse and repairing the damage he had done - back to Cybertron to aid the Autobots in the quest for the keys.
Eventually, despite continued attempts by both Megatron and Starscream to steal the power of the Cyber Planet Keys, the Autobots were able to gather the keys from Velocitron, the Jungle Planet and Earth, and brought them and their focusing device, the Omega Lock, back to Cybertron. Coupling these three keys with the power of the Matrix, Optimus Prime was able to initiate Primus' transformation from planet mode to robot mode. Communicating with the Autobots through the Mini-Con, Jolt, Primus explained that the destruction of Unicron, the embodiment of the force of evil, had unbalanced the universe, and that only he could seal the black hole and restore order - but to do that, the fourth Cyber Planet Key, from Gigantion, the Giant Planet, was required to reconnect Primus's spark with his body and restore his full power.
Attempting to retrieve the Omega Lock, Starscream made a rather pointless attack on Primus, only to be smacked down hard. Shortly thereafter, when Primus was in the process of channeling some of his power into holding back the ever-growing black hole, Starscream tried again, plunging into the energy beam and absorbing some of Primus' power into himself. Starscream expanded in size until he was as large as Primus himself, but Primus did not take this slight lightly, as he converted Cybertron's moons into a pair of mace weapons and relentlessly pounded Starscream into submission.
Eventually, the Autobots were able to acquire the final key, as well as to reactivate the four ancient ships which had carried the keys to the respective worlds ages ago - the Atlantis, the Lemuria, the Hyperborea and the Ogygia. Primus fused the four ships together to form the Ark, and with his powers subsequently restored by all four keys, he channeled all of his power through the Ark as a beam, straight into the heart of the black hole. With a massive blast, the black hole was finally sealed, and Primus transformed back into Cybertron - not Cybertron as it had been, but a new Cybertron, infused with the differing aspects of Velocitron, Jungle Planet, Earth and Gigantion, a true paradise for Transformers and humans alike.
While the Autobots were occupied with the quest for the Cyber Planet Keys, Unicron's heralds Ramjet and Nemesis Prime arrived on Cybertron, intent on unleashing the Dead Matrix - as the Matrix was the antithesis of Unicron, so too would the Dead Matrix ensure the destruction of Primus, thereby totally destabilizing the multiverse and reducing it to a sea of entropic chaos. For the first time, it would be possible for Unicron to strike at Primus in all realities simultaneously, ending their cosmic feud once and for all.
Ramjet and Nemesis Prime were ultimately stopped by Vector Prime and allies Sentinel Maximus and Omega Prime, plucked from the midst of the Universe conflict by the multiverse-warping energies of the black hole. The Dead Matrix, however, was cast into the heart of the black hole by Unicron's servant Soundwave, freeing Unicron's spark and allowing it to adopt a new, diminutive physical form. Unicron participated in the escalating Mini-Con civil war on Cybertron's moons, but when the planet transformed into Primus' robot mode, Unicron fled. His whereabouts are unknown.
Kiss Players continuity
While on an adventure through space and time, the singing group known as the Kiss Players - natives of the Generation One universe - were accidentally scattered across the multiverse, and found themselves in the Unicron Trilogy universe. Shaoshao Li and Zangetsu found themselves stranded on the surface of Cybertron, where they were menaced by Scrapmetal. Shao was rescued by Safeguard, who told her that she stood upon Primus himself. Shortly thereafter, with help from Vector Prime, the giant golden hand of the Primus from her native universe took her back home.
IDW comics continuity
As of this writing, neither Unicron nor Primus has appeared in the new IDW comics universe. Writer Simon Furman has outright said that this universe will have "no Primus. No Unicron", while hinting IDW may be "poking and prodding around the pre-history of the Transformers... the very beginning".  IDW publisher Chris Ryall has also stated "we're also going to do the TF origins this year , too. That one will be called The Thirteen". 
While author intent on its own could still leave room for an IDW Primus, if the upcoming story has a contradictory origin for the Transformers, that would retcon out the previous retcon, rendering Primus as being once again a feature of only some Transformer continuities. (And then some poor sod would have to heavily edit this article.)
It is confirmed that there was a Primus in some shape or form, as Cybertronians were shown taking his name in vain while under attack in Megatron Origin, part 4. Furman's explanation for this in his blog is that this is not the G1 Primus, but it is possible there was "something or someone" called Primus at some point. 
In the absence of Primus, there were some other interesting things to mention in Cybertronian religion. In the Stormbringer miniseries, Jetfire and Scoop make mention of Primacron in an almost religious manner ("Primacron help us" and "Primacron only knows"). Bludgeon claims that there is a spirit of Cybertron which needs to be appeased to restore Cybertron, which one could easily interpret as Primus. However, Bludgeon's idea of appeasing Cybertron was to allow Thunderwing to destroy a bunch of planets in a mass sacrifice, so his sources (and his sanity) are a matter of debate.
Primus in Japan
While Primus has been a staple in Western Transformers fiction since 1988, the character has only recently made the leap across the Pacific to take part in the world of Japanese Transformers storylines.
Primus did not exist in Japanese Transformers fiction until he was introduced in Superlink (Energon). Although his nature is not fully divulged in the course of either this series or Galaxy Force (Cybertron), some early Superlink pre-production notes go into the specifics of Primus' creation. Not particularly in-line with the Western multiverse origin of the character, they present Primus as an entity consisting purely of energon. Energon, the notes state, is the product of the "genetic material" of the sun interacting with planetary bodies - this, then, appears to be a very literal interpretation of Primus' role as a "light god," presenting him as an actual product of the light of the sun.
Kiss Players/Teletraan Go! Go!
The Japanese decided at last to introduce a "G1" equivalent of the character in the Kiss Players fiction of 2007, wholly distinct from the version seen in Energon and Cybertron, since the character is not a multiverse singularity in Japan. Here, the character was envisioned as part of a complicated retcon that merged various animated concepts - Primacron's assistant, Vector Sigma and the Oracle - into one singular entity, who was also Primus.
Formerly the assistant to the Primacron, the ancient genius who created the giant mechanoid Unicron, the robotic being known as the Oracle was badly damaged when Unicron rebelled against his creator. His essence fled to a dead world at the center of the galaxy, which he used his powers to transform into a verdant, green planet. This world was eventually discovered by the alien Quintessons, and the Oracle was captured and transformed into the mega-computer, Vector Sigma. The Oracle's world was transformed into the metallic planet of Cybertron, his powers were harnessed by the Quintessons to create the races of robots that would eventually become the Transformers, and the shell that had held his essence became the Matrix of Leadership.
Eons later, in the year 2007, three of Unicron's servants, the Sparkbots, co-opted the human singing group, the Kiss Players, into helping them gather up the scattered essence of their master following his destruction in 2005. The three girls - Marissa Faireborn, Atari Hitotonari and Shaoshao Li - were taken on a journey through space and time, and were tricked into believing that they were recovering fragments of the so-called "Allspark" from Autobot or Maximal leaders throughout history. The Oracle - by this stage calling himself Primus - was forced to intervene, appearing as a giant golden hand which began to steal away the fragments before the Kiss Players could gather them. Pursuing him across the multiverse, the Kiss Players collided with the Wall of Time and were scattered across dimensions.
Primus rescued the girls from the Unicron Trilogy universe and revealed the Sparkbots' deception, before transforming into his "golden ark" mode (which Shaoshao thought looked more like a camper truck) to pursue the three villains back in time to prehistoric Earth. They arrived just in time to witness the Sparkbots' successful restoration of Unicron to life, but Primus transformed once more and unleashed the power of his mobile cannon platform, destroying Unicron's energy and sealing it and the Sparkbots deep within the planet. To ensure that Unicron would never be freed again, he created a mighty guardian, Fortress Maximus, who would watch over it and the Earth. With the battle over, Shaoshao asked about the Kiss Players' future, but Primus did not reply. His work complete, the god transformed into a golden sphere and went to sleep.
War for Cybertron
A Decepticon brute thanked Primus that Megatron was still functional, seconds before he was killed by Omega Supreme. An Autobot soldier later yells "Thank Primus you're here!" at Optimus' arrival before being smashed by a brute. Optimus Prime also thanked Primus for the apparent victory over Trypticon, moments before the giant rose again.
Guess he doesn't like being thanked.
Billions of years ago, Primus and Unicron fought an evenly matched battle for supremacy. In order to best his nemesis, Primus created the Thirteen, and together they managed to defeat Unicron, who was in his weakened state and left to drift throughout the galaxy. Primus then merged with the already-existant Cybertron's core and lay dormant for many millions of years. As Cybertron entered and continued a civil war, the battle's began to poison the planet's core in turn infecting Primus. Luckily Orion Pax arrived to help clear the core of its affliction. Primus, sensing Orion's pure spark, bestowed upon him the Matrix of Leadership, containing the essence of the Thirteen original Primes, turning Orion into Optimus Prime.
- God Primus (2004)
- Accessories: Photon Eliminator, spoiler, 2 gun shields
- Unbeknownst to many Western fans, the first Primus figure was a "Lucky Draw" toy in Japan, a vacuum metalized gold chrome recolored Rodimus Prime that was given away as a contest prize from the collector book, Transformers: Generations. Supposedly, only 100 pieces of these lucky draw figures were manufactured.
- As a redeco of a Rodimus (no doubt inspired by the resemblance of his astral form to Rodimus in the UK comics), Primus transforms into a futuristic truck resembling nothing so much as a Winnebago. Following the trend started by Optimus Prime, his trailer splits down the middle to transform into a battle station with an extending double-barreled cannon. The figure comes with a large, hand-held blaster, and two blast-shield accessories that plug into the sides of his battle station cannon.
- Primus (Supreme, 2006)
- Japanese ID number: C-00
- Accessories: Omega Lock, special silver Cybertron planet-type Cyber Planet Key
- Primus was developed by Hasbro and Takara as a toy for their joint Cybertron/Galaxy Force toylines, but was released in Japan in the Generation One line a few months after Galaxy Force had ended its run. This release can be considered a pre-release of the Cybertron toy because it features Hasbro's Cyber Key Codes that the Galaxy Force line lacked.
- Primus is the first toy representation of the Transformers' creator as their home planet of Cybertron. In planet mode, he is considerably more detailed than Unicron from the Armada line, with visible cities, including Iacon, based upon its appearance in the DK Publishing book, Transformers: The Ultimate Guide, and Kaon as seen in The War Within. On the 'bottom' of the planet mode there are four hard rubber legs, molded to be shaped like towers, allowing Primus to be displayed in planet mode, yet not require a flat base as Unicron did.
- Primus' transformation is unusual, in many ways similar to a Powermaster, in that he requires the owner to insert his accompanying Omega Lock accessory into several special ports around the planet, then manipulate it to unlock his parts and transform him. When the Omega Lock is inserted into his back and pushed, a transforming sound is heard. When it is inserted into his chest and pushed up to reveal his head, his eyes glow red and a laser-type sound effect is heard. The Lock itself lights up red when it is inserted into any of the ports.
- In robot mode, Primus resembles both the Beast Wars Neo Unicron prototype as well as Don Figueroa's Primus concept, created for The War Within and used in The Ultimate Guide. He is bristling with weaponry, including two shoulder-mounted cannons that can fire missiles, two forearm blasters that raise and extend when a Cyber Power Key is inserted, and several banks of Gatling guns, lasers and missile launchers in his shins and legs revealed by the Omega Lock.
- Primus also has what might charitably be called a third mode - an intergalactic world-ship, which is basically formed by transforming the figure halfway and leaving the head down and the legs backward. It features no dedicated parts or transformation steps, making it very obvious that it was created after the fact. It looks kind of like The Starship Enterprise...backwards.
- Primus comes with two accessories, the aforementioned battery-operated Omega Lock that lights up red when inserted into any of the four Omega Lock ports, and a special silver Cybertron-Planet Cyber Power Key with the key code sp8u tampographed onto the back. Any four Cyber Planet Keys can be inserted into the four key slots at the base of the Omega Lock, though doing this does not activate any feature. There are also nine inactive Mini-Con powerlinx ports on the Primus figure, including two on the claws on his legs.
- Cybertron Primus (Supreme, 2006)
- Accessories: Omega Lock, special silver Cybertron planet-type Cyber Planet Key
- Cybertron Primus is the North American version of Primus, released a few months after the Japanese release. Both toys are identical.
- In North America, limited early-run versions of Cybertron Primus came packaged with a very creepy "battle damaged" Unicron head based upon his Armada appearance.
- A later version, exclusive to Wal-Mart as a Black Friday 2006 special, included four Mini-Cons; Strongarm, Knockdown, Nightscream, and Offshoot.
- The original form of Primus in Marvel Comic continuity is similar to Hot Rod/Rodimus Prime.
- The myth of Primus and Unicron bears a passing resemblance to the Zoroastrian myth of Ahura Mazda and Ahriman.
- The idea of Primus transforming bears some resemblance to an early script for the original movie, in which Optimus Prime merges with Cybertron and transforms into a super robot to defeat Unicron.
- In the cartoon Ben 10: Alien Force, there is an actual episode and artificial planet named "Primus".