The Spirit Guard are the end result of a plan that was hatched by a group of citizens of the Ardent Empire in a parallel reality.
The plan was developed as a last ditch attempt to save the "earth" from an invasion of 3 hostile groups from the ardent empire. The Royals, platicore and the Other Power, all of whom were at war with each other. The plan involved the sacrifice and reincarnation of the participants so that they could be reborn on "earth" after the doorway between the two worlds was broken. However, before they could seal off the doorway, Platicore, head of one of the warring factions, made it through the Standridge stones to "earth", where he went into hibernation to recover from the injuries he suffered during the war.
Now, each of the plan's participants were reborn and have come together in college. Because of their Ardent heritage, Empathokinetic abilities awoke in them all and thus they became the Spirit Guard. Currently, they fight monsters constructed by Platicore. These monsters drain people of their investiture, or energy, and return it to Platicore so he can heal. These monsters disguise themselves from the masses, but will actively attack the Spirit Guard.