Dark Energon (ダークエネルゴン, Dāku Enerugon) is a powerful, corrupted version of energon which can be used as a violent weapon and explosive. As energon is the emanation of Primus, from which all Transformer power and supply is formed, Dark Energon is similarly the emanation of Unicron, released after his first battle with the thirteen original Transformers. Even the smallest particle of Dark Energon can corrupt any amount of regular energon.
The violet-glowing Dark Energon supercharges any Transformer who ingests it, making them stronger, faster, more powerful...and more aggressive. It turns pain into pleasure, rendering any blows inflicted on a user futile and heals their wounds as well. However, it also acts as a powerful narcotic, filling the user with thrilling, dark sensations and causing addiction. Dark Energon withdrawal turns the user into a raving brute desperate to do anything for more. If the craving is not satisfied, the user devolves to a beast-like state and eventually dies.
Those who imbibe Dark Energon have been seen to project it from their bodies for various destructive purposes, such as attacking enemies, overloading computers, and bringing machines under their control. When a user is killed, the energy acts like a sentient thing (a worrying aspect for a force originating from Unicron) and flies from their corpse to empower any other user nearby.
Pieces of Cybertron infected by Dark Energon tend to turn purple and explode upward into twisted, sharp spikes and growths of metal. Some Dark Energon wielders have even shown the ability to detonate a cluster of these spikes in order to produce a group of mechanical spider-like creatures, which swarm anything nearby.
A Cybertronian corpse injected with Dark Energon will reanimate itself as a feral zombie, intent on destroying all in its path. They are mostly mindless berserkers, but can be commanded by a living Cybertronian who has also been corrupted by the evil energy.
Dark Energon was discovered over ten thousand years ago. When the Transformer race learned of its powerful yet volatile nature, it was sealed away in an orbital space station and placed under the watchful eye of the Seekers, including the scientific Jetfire and the former Sky Commander, Starscream. At some point, experimentation on Dark Energon began, and a small quantity of the substance became unstable. The resulting explosion ripped apart an entire section of the space station; a level of destruction beyond any weapon known to the Cybertronians. The horrors of Dark Energon were noted by many, such as Jetfire, and it was deemed that it must remain sealed for the rest of time. This continued to be the case for centuries, causing the existence of Dark Energon to become a myth that few believed.
After learning the existence of this substance, Megatron took a fleet of cruisers to lay siege to the station, crashing his own ship into it to gain entrance. Once inside, he had to battle the forces of Starscream and Jetfire, both of whom attempted to dissuade him, claiming that Dark Energon was impossible to control. As Megatron drew closer to the storage chamber, Starscream attempted to destroy the last remnants of Dark Energon, but Megatron was able to breach the core before the Sky Commander could complete the destruction. When the dark substance was finally revealed, Megatron, believing himself to be worthy of such a weapon, confidently immersed himself in it.
Despite Starscream's insistence that Dark Energon destroyed everything it touched, the Decepticon leader managed to control it, emerging more powerful than ever. His first act was to infuse Brawl and Barricade with Dark Energon; claiming it was their birthright. His second act was to cut through the final defenses between himself and the Seekers in a matter of seconds, thanks to his new power. Seeing Dark Energon being tamed, Starscream offered his services to Megatron, claiming he knew of an Energon Bridge that could produce more of the substance. Seeing this as an act of betrayal, Jetfire escaped the station in order to inform Zeta Prime of this treachery.
Shortly after this, Starscream, Skywarp, and Thundercracker travelled into the depths of Cybertron in order to reactivate the Energon Bridge. Facing many defenses and enemy Autobots, they managed to corrupt the central generator of the Energon Bridge. Fending off the initial infection, the core attempted to defend itself and purge the Seekers, but the evil planes quickly brought it down. This allowed the Energon Bridge to activate and beam its contents to the orbital station, allowing mass production of Dark Energon.
With mass quantities of Dark Energon in his possession, Megatron sought to control whole of Cybertron even if it means by to corrupt or infest the Core itself. To do so, he needed the Omega Key in order to get past the Omega Gate that barred entry to the centre of the Transformer homeworld. Thus, he assaulted Iacon in order to claim it from the Stellar Galleries. However, Zeta Prime learnt of this and spirited the key to be hiden away. During his journey to claim the Key, Megatron used his personal store of Dark Energon to corrupt doorways that blocked his entry, and his army made use of bombers carrying payloads tainted with the stuff. By this time, the Autobots had developed defenses against the Dark Energon Bombers (including auto-purging turrets and doors resistant to the energy), but the Decepticons were able to cut through them in short order.