Fi

Fi is a character featured in Skyward Sword who is the humanoid representation of the Goddess Sword. It 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 Goddess 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 Goddess Sword is helping Link, it will transform into Fi and will lead the young hero back and forth from Skyloft to the land below. Moreover, Fi has a "treasure-seeking ability" called Dowsing, where it can sense important items and inform Link about them. Fi is also the focus on the reason why there are two lands divided by a bank of clouds."

Gender
In an interview with Eiji Aonuma, he said that even though the Goddess 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

 * Fi 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, Fi speaks in a gibberish language. Fi's voice also sounds very synthesized. Additionally, its style of speech is rather emotionless and robotic.
 * Fi refers to Link as "Master".