Rarified Energon

Whereas normal Energon provides the fuel that keeps Transformers rolling along, Rarified Energon is something more. It is the base material of all Transformer life. Rarified Energon is the base of the Transformers' physical forms and the stuff of which sparks are made. Rarified Energon is also apparently of limited supply throughout the multiverse. If it all were to be used up, no more Transformer life could come into being. Given this, its protection is of vast importance to Primus, and he has tasked Nexus Prime of the original Thirteen Transformers with its protection. Crossing Over: Part 6

The Autobots would later move this resource frequently to keep it out of the hands of the Decepticons. However, Gigatron would manage to track its location to Ironworks. Invasion Prologue