The Keystone was a stone that unlocked the Codrex. There were six pieces that made up the keystone. These were given to several Av-Matoran
- A Keystone that was stolen from the Av-Matoran by the Phantoka Makuta.
- A Keystone that was formerly somewhere in the Swamp of Secrets that was acquired by Gali.
- A Keystone that was given to the Toa Mistika by an unnamed Av-Matoran who then transformed into a Bohrok.
- A Keystone that was formerly in Krika's base camp.