Transformers: Combiner Wars.

Forty years after the Great War on Earth, the Autobots and Decepticons are no more and Optimus Prime and Megatron are relics of the past. Cybertron is at last at peace, ruled by the triumvirate of Starscream, Rodimus Prime, and the Mistress of Flame. However, the Enigma of Combination, an ancient artifact of Primus, has triggered new conflict through the creation of huge, dangerous Combiners, and now Cybertron's fragile peace is in danger of collapse.