Earlier in 2008...

A few weeks ago, biomechanical humanoids named the Toa Nuva reawakened their "Great Spirit," named Mata Nui. In reality, this Great Spirit was a forty million foot tall robot whose body housed the universe of the Toa, Matoran, and the other inhabitants of that world inside. Unfortunately, a gaseous being, known as a Makuta in that universe, was able to hijack Mata Nui's body and possess the robot. This Makuta, named Teridax, had planned this for thousands of years. His only threat at that point in time was Mata Nui himself. So Teridax forced Mata Nui's spirit into the Mask of Life, the Kanohi Ignika, and shot it out into space, banishing it from the Matoran Universe.

However, during Teridax's takeover, a Keyblader was present in the universe. This Keyblader, named Pocamu, as well as his four friends, had fought alongside the Toa and the other inhabitants to defeat the Brotherhood of Makuta and reawaken Mata Nui. Unfortunately, they had all been tricked. Before Pocamu and his friends escaped, the Keyblader promised to find the Mask of Life and bring it back to the universe along with Mata Nui himself in order to defeat the evil Makuta Teridax. He then received a mask, a yellow Kanohi Hau, that once belonged to a great hero to give him luck on his journey.

As the Keyblader and his friends tried to escape through a dimensional portal, Teridax attempted to interfere and separated Pocamu and his friends. Pocamu ended up three years in the past in a place called Castle Oblivion while his four friends, the Dezenta, were sent to a world known as Twin Skies in the present. Unfortunately, the Dezenta's memories were lost and their bodies took new forms...