The Goddess Sword was a divine weapon created by the goddess Hylia to aid the chosen hero in defeating the evil demonic forces led by Demise. Link, the hero chosen by destiny, retrieves the Goddess Sword from the Statue of the Goddess in Skyloft, which starts the long journey of forging the Goddess Sword into the Master Sword
In order for the Hero of the Sky to transform the Goddess Sword into the Master Sword, they must infuse it with three sacred flames, each guarded by a powerful spirit in different regions of the world. Once the sword has been imbued by the three Sacred Flames, the sword transforms into the Master Sword. After Zelda shares with the Hero of the Sky that she is the Goddess Reborn, she blesses the sword, unlocking its full potential as the True Master Sword.