How about Vakama, after he arrive on Spherus Magna, saw a big enemy, one who would kill most of the Toa, so he craft a armor for a new Toa. The mask was fused by the Vahi. Then Vakama used a power source (I don't know what) and make the armor alive, with organs and everything. How about the big enemy was the female version from another dimension? In the last battle, the Toa sacrifice himself to create an explosion who killed the enemy. The original Vahi arrive at the Turagas and the other part, the one fused with the original, arrive at Ekimu.