Synopsis of Transformers: Revenge of the Fallen
In 17,000 B.C., the Primes (the highest ruling Cybertronians) gather their energy, Energon, from sun harvesters, machines that consume stars to harness their energy.
The Primes have a sacred rule to never deplete a star that sustains life. One Prime violates this rule by building a sun harvester on Earth, for which he was defeated by the other six Primes, and becomes "the Fallen", the original Decepticon.