Sols are spherical light sources that can be found within the Palace of Twilight in Twilight Princess. They are similar to the sun in the Twilight Realm. Like the sun, they are a source of light, life, and energy.They can activate many pieces of Twili technology when placed inside certain pedestals, as well as banish darkness.
Once Link enters the Palace of Twilight, he finds that the sols have been locked away by Zant, and that he cannot enter the main part of the castle without first acquiring the sols, and placing them in the correct pedestals located near the entrance. There is a sol located in to east wing, and one in the west. Each are guarded by Zant's Hands, and Link must grab them and escape while avoiding the hands, who will chase Link relentlessly in an attempt to get them back. Once Link has returned both sols to the entrance, he will be able to change the mutated Twili back into their original forms, and once placed in their pedestals, the sols infuse Link's Master Sword with light, creating the light sword, which allows him to cut through the dark fog found in the Palace of Twilight.
Zant's Hand guarding a Sol