Fi

Phi is a character featured in Skyward Sword who is the humanoid representation of the. She is the spirit within the sword and guides Link during his adventure, serving as the young hero's companion in the game.

History and Abilities
The Skyward Sword is located in the floating island known as Skyloft; however, Link eventually finds the sword and uses it to travel between two lands: Skyloft, an island floating above the clouds, and Hyrule, which is being ruled by evil forces. According to Eiji Aonuma, when the Skyward Sword is helping Link, it will transform into Phi and will lead the young hero back and forth from Skyloft to the land below. Moreover, Phi has a "treasure-seeking ability" where it can sense important items and inform Link about them. Phi is also the focus on the reason why there are two lands divided by a bank of clouds."

Gender
In a recent interview with Eiji Aonuma, he said that even though the Skyward Sword transforms into a feminine figure, he revealed that he does not consider it as a female person. For now, it seems that this entity is genderless.

Trivia

 * Phi bears a striking resemblance to the Fairy Queen from The Wind Waker and Four Swords Adventures. The reason for this, if there is any, is not yet known.
 * Just like Midna did in Twilight Princess, Phi speaks in a gibberish language. Phi's voice also sounds very robotic, speaking in a synthesized voice. Additionally, her style of speech is rather emotionless and robotic.