Instructions
Collect 340 Light Seeds. Light Seeds are scattered throughout the game in small groups. Consult the Light Seed guide (see link under Resources) for specific Light Seed locations.
Return to the temple, and stand on the yellow plate.
Press the "Triangle" button (if you are playing the PS3 version), or the "Y" button (if you are playing the Xbox 360 version), in order to activate the third power.