Lorien was once a peaceful planet flourishing with life. It was inhabited by beings with indistinguishable similarities to humans. There were two types of Loric citizens. One group were called Garde. They possessed special abilities, called legacies, which were used to defend the planet. The other group, called Cepan's, lacked in these special powers. They were each assigned a Garde child to mentor and, during teenage years, help to develop their legacies. The system worked for thousands of years, however a great unrest was growing amongst the Cepan. They felt oppressed by the Garde and a large number formed a rebel group. An uprising began which led to a devastating war. The Cepan fought the Garde with nuclear weapons, destroying the luscious green planet and turning it into a desolate, uninhabitable rock.
Amidst the chaos, twelve Garde children were evacuated by spaceship with their twelve Cepan protectors and sent to Earth, a supposed safe haven. They arrived on the only land mass that was occupied by humans, a country called Panem. There were 12 districts, ruled by The Capitol. Their Cepan realised that Earth was a dangerous place for children with special abilities. They decided to go their separate ways, taking each child to a different district. There they would wait until each child had begun to develop their legacies. Only then would they reunite and return to Lorien to rejuvenate the planet using the Garde's powers. For their own safety it was agreed that the children would not know the truth of their origin until they came of age.
For anyone who hasn't read the Lorien Legacy books or watched I Am Number Four, I believe it isn't essential in understanding this story as I've aimed at this audience. However, if I've left any gaps or you're finding yourself confused, please let me know and I will clear things up or explain those things in the next chapter.
I've already mapped out a sequel to this story, set during Catching Fire. There the other Garde will play larger roles. So if people like this fic, I'll hopefully continue with two more sequels :)