Oathkeeper

The Oathkeeper (約束のお守り) is the Keyblade that represents Sora's friendship and memories of Kairi. Gained by speaking to Kairi in the Secret Waterway in Traverse Town, after her rescue in Kingdom Hearts, it takes on special significance as the keychain that forms it is Kairi's Lucky Charm, which she makes Sora promise to bring back to her. As a result, Oathkeeper is one of the few alternate forms of the Keyblade with an impact on the Kingdom Hearts storyline.

It serves as the counterpart to Oblivion, the Keyblade that represents Riku; it can also be seen as a Keyblade of Light, to balance out Oblivion's Darkness.

Oathkeeper is also one of two Keyblades Roxas wields when he is at his most powerful. He bears it alongside Oblivion; together, they represent his ties to Sora through Riku and Kairi.

Appearance
The Keychain motif is of Kairi's Lucky Charm; a Paopu fruit-like star made of thalassa-shells. Its shaft displays two hearts, and its handle bears two angel wings, contrasting the bat wings that comprise Oblivion's handle. The teeth are fashioned in the shape of the Kanji for "light" (光), corresponding to the Oblivion's Kanji for "darkness".

In Combat
It has a decent reach and is well-balanced in Kingdom Hearts; Oathkeeper is a good substitute for the Lionheart, in case the player hasn't been able, or didn't want, to defeat Cloud and Leon in the Hades Cup. In Kingdom Hearts II, its ability of Form Boost makes it much more useful for leveling Sora's Drive Forms, rather than for regular battle.

Other Appearances
A limited edition Oathkeeper was released with four other Keyblades in a special Play Arts Figures accessory set, Play Arts Arms.