Quick recap
With Megatron dead, the Autobots and most of the Decepticons try to rebuild Cybertron. Unicron returns, possessing Megatron's body, and sets out to destroy the planet's core, which is Primus. Optimus and Wheeljack go looking for the AllSpark while the others hunt Shockwave and Starscream, who have created new Predacons. Unicron beats Predaking and raises the dead of a Predacon graveyard as Terrorcons, so the Autobots must team up with Predaking, Skylynx and Darksteel. At the Well of AllSparks, Unicron moves to claim the container, but his Anti-Spark gets pulled inside, sealing him away for good. Freed, Megatron disbands the Decepticons and goes into exile. Optimus reveals he stored the AllSpark inside the Matrix and can't separate them. He plunges into the planet's core, millions of sparks are reborn, and his goes with them.