Keyblade of heart

The Dark Keyblade (also refered to as "Artificial") was an officially nameless Keyblade made out of the six hearts of the Princesses of Heart. It had the power to unlock people's hearts and was used by Riku when he was possessed by Xehanort's Heartless. Riku first used it to unleash Maleficient's dragon form, then wielded it in combat against Sora. This Keyblade disappeared when Sora stabbed himself with it to free Kairi's heart.