Going to divide this one into 2:

Bohrok Kal:
After the encasement of the Bahrag, the Toa Nuva enjoy a short time of peace and letting their village know they've changed. However, the Bohrok Kal have awakened to free the Bahrag, first by getting the Nuva Symbols, find the Bahrag, and insert the symbols to a cube to free them. The theft of the symbols makes the Toa Nuva lose their elemental powers, and they must desperately get them back. The first encounter was a defeat for the Toa Nuva, but when they all get to where the Bahrag are held, the Exo-Toa from previously attack the Kal hopelessly. Then Tahu Nuva reveals the Mask of Time he has. Using it, he slows down time, but by that time, the Bohrok Kal have their Krana into Sterling Silver type, shielding them in a force field, and they are almost unlocking the cube. Gali Nuva's quick thinking made the Kal gain so much power they lost control. Thankfully, it defeated the Kal by their own powers. The Toa Nuva regained their powers and they leave the place.

The Mask of Light:
I'm too lazy to type the summary, so go here.