At the beginning of the Ignition Saga, the Piraka invade Mangaia and Teridax plants the knowledge of the Kanohi Ignika in their mind. He uses the Skakdi to transport his essence to Voya Nui, but why did he need them past that?
He clearly needed the toa to use the mask of life to save Mata Nui as per the Mahri story and his interactions with Matoro, but as far as I know he was not expecting the toa inika to arrive/be formed. As far as he knew, the toa nuva would have remained defeated by the Piraka, and Mata Nui would have died—ruining The Plan.
So, why did he help them? Could he have tricked the Piraka into using the mask to save mata nui? Can Skakdi use mask powers? Would he have tried to use the mask himself?