White Sword of the Sky

The Goddess Sword is an item featured in Skyward Sword. First introduced in a leaked E3 2009 artwork, it is inhabited by a spirit known as Fi. Eventually, the Goddess Sword becomes the Master Sword.

History
The Goddess Sword rests in the Statue of the Goddess on the floating island in The Sky known as Skyloft. Preceding the Wing Ceremony, Fi appears to Link in his dreams, foretelling him of his destiny. After Link and Zelda are attacked by a black tornado, Link wakes up in his room, where he hears Fi speaking to him. Fi guides him to the Inside of the Statue of the Goddess and further explains his fate as a hero and encourages him to draw the Goddess Sword from its pedestal. Fi gives Link the Emerald Tablet and tells the young hero that he must go beneath the clouds in order to find Zelda and fulfill his destiny and that the Emerald Tablet will guide the way.

Later, Link must temper the Goddess Sword using sacred flames, first being tempered by Farore's Flame, resulting in the Goddess Longsword. Then it must be tempered with Nayru's Flame, creating the Goddess White Sword. After it has been tempered by Din's Flame, it become the Master Sword. Once the Master Sword has been blessed by The Goddess, it becomes the True Master Sword.

Powers and Abilities
When the Goddess Sword is helping Link, it transforms into a humanoid figure and lead the young hero back and forth from Skyloft to the land below. Moreover, the sword has a "treasure-seeking ability" called Dowsing. It can sense important people and items and inform Link about them. When Fi has something to say, the sword begins to glow.

If Link holds the sword up to the sky, it will be charged up by "energy from the heavens" and be able to release a Sword Beam once it's swung. This beam can activate Goddess Cubes, sending them into the Sky.

Theory

 * Hylia's primary antagonist, the Demon King Demise, possesses a sword that seems strikingly similar to the Master Sword. It remains unexplained whether the blade wielded by Her Grace and her chosen hero was specifically created to counteract Demise's weapon or vice versa. This is made further unclear by the fact that Fi and Ghirahim are similar humanoid beings accompanying each sword.