So in order to write today's review of Mata Nui, I had a lot of catching up to do. The last time I was involved in the Bionicle story was back when they introduced Metru Nui, in 2004. For info on everything leading up to that point, read our five Bionicle Primer Courses:
So, after that. The Toa Metru returned to Metru Nui after escorting all the Matorans to Mata Nui (the island, not the character). The city had been overrun by plants and spiders, and they were mutated into 2005's Toa Hordika sets: the ones with the flying discs launched from their backs.
In 2006, the flashbacks were over, so the original Toa Nuva went to try and wake up Mata Nui (character, not island) using the Mask of Life. Learning about the mission, a group of Matorans followed them, and were struck by magical lightning and turned into the Toa Inika, so they could fight the Piraka. The mask fell into the deep waters, so they followed, and were mutated into the Toa Mahri, and had to deal with the Barraki, underwater warlords who wanted the mask for themselves.
2008's story took place in Karda Nui, which is where the Phantoka and Mistika groups come from. With Mata Nui almost dead, Matoro (one of the Matorans struck by lightning) sacrificed his own life to bring the Great Spirit back to life - but it was in that brief period that Teridax, the Big Bad, plunked himself into the driver's seat, so that when the Toa succeeded in reawakening the body, he'd be in charge.
So that, in short, is the extremely truncated version of what I missed. There's a lot more to it, like the island Mata Nui actually being a camouflage reaction on the character Mata Nui's face, and the destruction caused by the Bohrok way back when was a natural process, designed to clear all the crap off the island so the big guy could wake up. We could probably fill an entire PoA with all the info, but this is the quick and dirty version. Any questions?