Armor of Unicron
From MediaWiki

Megatron has always sought power at every turn, and this is one of the most striking examples of success. After escaping from the collapsing Energon Sun created to contain Unicron's spark, he had stolen most of what remained of the Chaos-Bringer's power, and his body had been rebuilt with salvaged pieces of the destroyer's armor.[1]
Fiction
Ask Vector Prime
After a mighty battle that pitted the Autobots against the Decepticons and Unicron, Megatron sought more power and searched for the remnants of the disembodied Unicron's spark. From this "lost spark", Megatron forged new armor, being reborn in a new body. Ask Vector Prime
Cybertron cartoon
Notes

- While the design cues from Armada Unicron in Megatron's Cybertron character model are hard to miss, the "Armor of Unicron" explanation did not make it into the text of the series until the bio of his toy's American release in one of many changes from Galaxy Force re-aligning the series to hew closer to Hasbro and Takara's original concepts for a sequel to Armada and Energon.


