Keyblades are a huge part of the story of Kingdom Hearts. There are two main ones, the one that Sora has, the Kingdom key (not including all the "keychains") and Riku's Key to Hearts that he tried to unlock Sora/Kairi's heart with to open the Final Keyhole thing. Riku/Ansem uses it to both fight and to unlock people's hearts to darkness with it in the game. In the secret ending thing, you can see that there are even more keyblades.