The Star Seeker is the first keyblade that Sora obtains in Kingdom Hearts II after his original keyblade, the Kingdom Key. It is given to him by Yen Sid after his new clothes are created by Flora, Fauna and Merryweather, and he is given the ability (by using a drive form) to wield two keyblades at once.
The Star Seeker is part of a group of weapons associated with Yen Sid's tower, along with the corresponding staff (the Comet Staff) and shield (The Falling Star). These weapons are decorated with crescent moons and stars, and are the second weapons available to the party. The keychain design is a crescent moon.
Appearance in Final Mix
In the secret ending movie of Kingdom Hearts II: Final Mix, Mickey is briefly shown, wearing a different outfit than usual and wielding the Star Seeker. The shot is brief, and no context is given, nor an explanation of the shot's relation to the battle that occurs earlier in the video. Some fans have speculated that the shot of Mickey shows him during his apprenticeship to Yen Sid, since the keyblade he wields is associated with the sorcerer.