Plasma energy is one of the most powerful and dangerous sources of energy in the galaxy.
American animated continuity
The power of plasma energy was harnessed by the Quintessons to create the Plasma Energy Chamber deep within Cybertron, the furnace in which the bodies of their robot creations were forged. When the Transformers subsequently took power on Cybertron, the special key needed to open the chamber was put in the care of the Autobots, with each leader charged to keep it safe.
Plasma energy seeks out and overloads any mechanism that converts matter into energy, making it lethal to Transformers. Organic life, for whatever reason, is immune to its effects, even though it falls into that category.
In 2007, Galvatron led an assault on Autobot City with the sole purpose of stealing the key and activating the chamber. Pounce and Wingspan were able to purloin the artifact, and the Decepticon forces then made for Cybertron, where Scourge was dispatched to activate the chamber. Pursued by an Autobot shuttle, Scourge was able to use the key and open the chamber, only for a bolt of plasma energy to knock his systems offline and overload the shuttle engines, blasting all onboard the other side of the galaxy, where they crash-landed on the planet Nebulos.
The Decepticons pursued the Autobots to Nebulos and were able to retake the key, prompting the Autobots to team up with a group of Nebulon rebels to become Headmasters. Arcee stole the key back from Scourge, but the Decepticons replicated the Headmaster process with the evil ruling Nebulon Hive and captured Arcee and Daniel Witwicky, returning to Cybertron. To save Daniel from torture, Arcee relinquished the key.
In the meantime, Galvatron had arranged for the construction of a gigantic rocket engine on Cybertron's surface, which propelled Cybertron into Earth orbit once again. With the key returned to him, the full scope of his plan was revealed - having abandoned hopes of conquering Cybertron or Earth, he now sought to use the plasma energy to overload the sun and drive it nova, that it might consume and destroy both planets in one strike. The chamber was opened accordingly, but the Decepticons' departure was briefly delayed by a battle between Scorponok and Fortress Maximus. Once the Decepticons had boarded and taken off, however, Scorponok was struck by a tendril of plasma energy and sent hurtling off through space. The Autobots, meanwhile, were left disabled by the plasma energy, leaving only the Nebulons and Spike Witwicky to save the day - by reversing the mechanism of the rocket engine, they were able to prevent the nova by draining off the excess solar energy, which they then used to revitalize Cybertron and restore its Golden Age.
Beast MachinesHaving hacked the Oracle, Tankor sent Optimus Primal a counterfeit vision telling him about the Plasma Energy Chamber. Primal was able to use the power of the Oracle to activate it, and he decided to keep that ability in his back pocket as a weapon of last resort against the Vehicons. He knew it would have global effects, but it also fit with his goal of restoring organic life on Cybertron.
Meanwhile, Megatron was mass-producing an arsenal of Keys to Vector Sigma as his own anti-organic doomsday weapon. When Primal raided his citadel for a face-to-face confrontation, the two called each other's bluffs and unleashed their weaponry. The planetwide collision of the two opposed energies threatened to destroy the world. Primal, however, was able to channel all of the energy into the Oracle and save the planet, at the cost of his own life. Megatron and Tankor, who were in the same room, were also destroyed. But while Rhinox's spark returned to the Matrix, Megatron's spark was somehow shunted into a new, fully bestial form.
Japanese animated continuity
Plasma energy is born of a cycle of continuous destruction. It is a force of pure planetary destruction, forged in the crucible of a word reduced to ash, and a small fraction of the energy released in such a horror is enough to devastate another world and generate yet more, continuing the chain of devastation. While Decepticon leader Galvatron may be content to toy with mere energon as he pursues his goals of conquest, Headmaster leader Scorponok knows that only through the manipulation of plasma energy’s deadly powers can galactic domination be achieved.
During the Decepticons’ attack on Cybertron to acquire the powerful new alloy cybertonuron, Scorponok saw his opportunity to seize power. Equipping Mindwipe with bombs, he dispatched him into the depths of Cybertron, ordering him to plant them in Vector Sigma’s chamber. Once detonated, it would completely devastate Cybertron itself, generating vast reserves of plasma energy that he could use for his own ends. Confronted by Galvatron over his actions, Scorponok offered the false rationale that this would prevent the Autobots from retaining control of the cybertonuron if the Decepticons failed to seize it; the enraged Galvatron headed for Vector Sigma’s chamber in order to defuse the bombs, but arrived just as they exploded, reducing Cybertron to a burnt-out husk.
With the plasma energy released in Cybertron’s destruction stored, Scorponok schemed to use it to generate yet more plasma energy. Installing himself as Decepticon leader, he began seeding the planet Mars with plasma energy bombs, intending to destroy the planet like Cybertron before it. Although his plans were discovered by an Autobot geological survey that was on the planet at the time, a blast of weaponized plasma energy prevented Autobot leader Fortress Maximus from transforming, leaving Scorponok – now bonded to his own giant Transtector – to pummel him as the countdown to Mars’s destruction began. Two clusters of bombs at the planet’s pole were detonating, beginning a chain reaction that tore Mars apart; Fortress Maximus was able to absorb some of the energy released in the early stages of the conflagration, allowing him to escape, but once again, Scorponok had achieved his goals.
Those goals, however, were soon put on hold with the surprise return of Galvatron, who retook command of the Decepticons and set them on an interplanetary energy gathering quest. When Galvatron was later defeated in battle by the Autobot Headmasters, Scorponok retook his position as emperor and, after a campaign on planet Master, returned to Earth intending to destroy it and acquire its plasma energy. “Death Towers” forged from the crysmag metal of Lemuria threatened to tear the Earth apart (exactly why Scorponok didn't use more plasma bombs isn't explained), but Fortress Maximus was able to stop the villain’s scheme and permanently exile his Decepticon forces from Earth.