Unicron, running out of energy, sends its slave robots to attack Earth and find more energon. This seriously jeopardizes the peace between the victorious Autobots and Decepticons who were forced to give up their evil ways.
Terrorcons attack energon mines on Mars and earth's moon: Optimus' team respond, but are too late to help Mars and fail on the moon. Believing earth to be next, Alexis orders the evacuation of Ocean City.
The Quintesson Alpha Q revives Scorponok, who abducts TidalWave to help steal Autobot energon in order to resurrect Megatron, currently in stasis inside the destroyed Unicron's head. Earth's Desert City is attacked this time.
Alpha Q gives Scorponok the Star Sabre, pulled from Megatron's body, as a reward for stealing the energon from the Autobots' Mars City mine. Three minicons from Mars can combine to form the Energon Sabre to combat its power.
Kicker the human energon detector finds an energon point in snowy mountains. From Cybertron, his father sends Cybertron City through a space bridge to settle over the point, crushing the attacking terrorcons in the process.
New, improved Autobot defences have stopped the terrorcons from stealing energon, and Alpha Q is getting desperate. Scorponok drives the Star Sabre into Megatron's spark, intending to kill him, but resurrecting him instead.
Starscream - invisible and incorporeal, incompletely resurrected due to insufficient energon - hunts for Optimus through Ocean City. Prime leads him through a space bridge to the moon, where battle continues until Megatron arrives.
Starscream heads for Asteroid City, followed by the Autobots. The Decepticons attack Lunar City, believing the 'Bots to be there. Prime learns of Alpha Q's ultimate plan. Dr Jones reveals his plan for an invincible energon net over earth.
With stolen Martian energon Megatron creates a mobile fortress and heads to earth. Alpha Q sends terrorcons for more energon for Unicron. At Ocean City, the newly-built energon tower deploys a 'shockwave assault', driving off the enemy.
As the latest energon tower is raised in Jungle City, Alpha Q's terrorcons attack, closely followed by the Decepticons. The tower is destroyed, but Optimus prevents the mine being looted by taking drastic action.
Megatron sends three artificial comets to devastate earth so he can steal its energon. The final energon tower, needed to fire up the energon grid that will prevent the disaster, is malfunctioning: Kicker goes to fix it.
The Miranda 2 spacebridges to a frozen, blizzard-swept but energon-rich world, where it wedges between two ice sheets. Inferno and Misha's attempts to dislodge it are hampered by the Decepticons and Alpha Q's new terrorcons.
Prime's plan to use the Miranda 2's energon grid to destroy Unicron's body from within fails: instead, they lure it through a warp gate to Cybertron, where the planet's newly-constructed energon grid severely damages it.
Kicker and Misha learn that Alpha Q destroyed his own homeworld in order to knock Unicron into stasis and stop him from devouring more planets. Meanwhile, on Cybertron, the vicious Shockblast breaks free from his prison.
Shockblast disables Cybertron's energon grid by shooting two of the towers, allowing the Decepticons to rescue him and regroup to prepare to attack. Unicron's head warps to Cybertron and Prime and Rodimus go to speak with Alpha Q.
Decpticons fleeing Cybertron join Megatron and are almost immediately spiked and their energon sucked to feed Unicron's body. Before the same thing can happen in Unicron's head, Prime returns with Arcee, who leads the Omnicrons to feed him.
Megatron sends terrorcons to steal energon from Primus himself, deep in the core of Cybertron, to reanimate Unicron's body. Alpha Q crashes Unicron's head into his body to allow the Autobots to reach Megatron.
Megatron releases the energon from Unicron's body: Alpha Q also releases the energon from Unicron's head. The two react and form a rift in space, which sucks in all of Unicron. Megatron, Prime and the Miranda 2 follow.
On the other side of the rift, the planets Unicron devoured have been resurrected and are absorbing energon into their cores. Scorponok, now under Megatron's control, arrives with his terrorcons to steal it.
Inferno guards the chained Shockblast on Iron Planet: Megatron eventually arrives and frees him to capture his erstwhile guard. Once caught, the autobot is tortured by Megatron. Meanwhile the Miranda 2 lands on a beautiful pristine world.
The Omnicons discover Jungle Planet's sun can produce energon. While Inferno struggles to overcome Megatron's programming and remain an Autobot, the Decepticons arrive to steal the planet's energon, and the battle continues.
Scorponok and his terrorcons remove all the energon from Iron Planet, causing the planet's destruction. The only way to save Jungle Planet from the same fate is to install an energon tower - but can the Autobots get it there in time?
Energon towers are installed on Rock, Blizzard and Ocean Planets, but Mirage damages the Ocean Planet one. As the Decepticons attack, Inferno, still struggling with Megatron's programming, acts as decoy to allow time for it to be replaced.
Rodimus authorises some Autobot r'n'r on a planet consisting entirely of race track. Ironhide's self-confidence improves. Meanwhile, Unicron is growing stronger as the Decepticons continue feeding him stolen energon.
Deep within Cybertron, Dr Jones witnesses the reactivation of Omega Supreme, ancient guardian of energon. Using the energon released with the destruction of one of Alpha Q's planets, Unicron's body is almost ready for action.
With Megatron urging him on, Unicron's body retrieves its head as the Autobots battle to prevent it happening. Whole again, Unicron pauses to recover, while Optimus learns he can powerlinx with Omega Supreme.
With Megatron now effectively under his control, Unicron destroys Blizzard Planet to gain more energon then turns to Circuit Planet. The Autobots fight but are defeated until an energy pulse from Primus re-energises them.
Powered up and now the same size as Unicron thanks to Primus' energy blast, Optimus Supreme battles the god, backed up by the re-energised Autobots. But with Megatron sharing Unicron's mind, can he truly be destroyed?
With Unicron's body destroyed and the war, seemingly, over, the Autobots start repairs on Cybertron. But Megatron survived, and follows a voice in his head to a vast pool of energon deep within the planet, watched over by ancient guardians.
Against the guardians' advice, Megatron immerses himself in the pool of super energon, transforming himself into Galvatron. As the Decepticons battle to take over Cybertron, Galvatron invites Starscream to prove his loyalty and also bathe.
Galvatron uses the super energon to set Cybertron in motion, heading for Alpha Q's planet. Kicker, Arcee and the Omnicons, who are immune to the energon gas, land on the planet to seal the breach in the gas line so the Autobots can return.
In a virtual training exercise pitching everyone against everyone else, even allies on the same sides, the action consists mainly of powerlinking and transforming, with a little actual fighting in between.
As Cybertron approaches the warp gate, the battle continues, now with hordes of super-energon-enhanced terrorcons in the way. Primus aids Optimus, who combines with Omega Supreme and reveals a new ability, blowing Galvatron away.
Cybertron exits the warp gate, destroying planets as it goes. The Autobots try to stop the planet heading for Plains Planet. Prime realises Unicron is still in play: Primus helps him stop Cybertron, but at what cost?
Increasing in size and power even further, attempting to become Unicron, Galvatron tows Cybertron behind him, heading into space. Kicker and the Omnicons sever the energon bands holding the two together.
While Prime and Galvatron, now both grown to immense size and power thanks to Unicron's influence, fight their final battle in space and then on Jungle Planet, the Omnicons fuel Primus and Kicker, sensing Unicron, searches for his spark.
The Autobots donate their sparks to Prime, to give him the power to fight the Unicron-possessed Galvatron. Primus forms the super energon into the basis for a sun which, with Galvatron's help, brings life to all of Alpha Q's planets.