So....My theory is that the Toa were taken after the rebirth of Spherus Magna, brainwashed (like always, maybe they'll regain memory, or glimpses, or something), and sent off to another planet that was in need of help (Maybe this happened to the Toa before Mata Nui, maybe this actually happened before Mata Nui). Anyways, the Toa are supposed to be heroes, traveling around and helping anyone who needs it.