Keystone

The Keystones were six pieces of a tablet detailing the way that the Great Spirit Mata Nui was to be awakened that was kept with Av-Matoran. Over the years, the tablet was broken and the pieces were lost. According to what Kopaka could read after obtaining three of the pieces, the Keystone said that the secret to reviving Mata Nui was in the swamp below Karda Nui.

Below are the locations of the six pieces and current status of each piece.

Strangely, in the comics, the keystones are shown as six pieces of a square tablet that fit in the torso part of the picture of Mata Nui, but in the mini-movies, it is shown as six pieces of the entire picture, not just the torso.
 * 1) Formerly with Solek, now with the Phantoka Toa Nuva.
 * 2) Formerly with Kirop, now with the Phantoka Toa Nuva.
 * 3) Formerly stolen from the Av-Matoran by the Phantoka Makuta, now with the Phantoka Toa Nuva
 * 4) Formerly somewhere in the Swamp of Secrets, acquired by Gali and now with the Mistika Toa Nuva.
 * 5) Formerly with an unnamed Av-Matoran; now with the Mistika Toa Nuva.
 * 6) Formerly in Krika's base camp; now with the Mistika Toa Nuva.