Fi is the humanoid representation of the Goddess Sword in Skyward Sword. It serves as Link's companion and assists him throughout the game. Fi gives you multiple options of help you can choose from during your journey. Fi and Ghirahim both share one characteristic: they dwell inside of extremely powerful swords. Fi, the "Goddess Sword" (Eventually advances to the "Master Sword"), and Ghirahim nests in a sword of more wicked attributes, that is possessed by the Demon King Demise.