Keyblade

Keyblades are key-shaped melee weapons created to fight darkness; they are the only thing that can free a heart from a Heartless and so allow a complete being to be restored. They can also lock and unlock doors and keyholes, and in the first game sealing a world's keyhole keeps the Heartless from destroying that world. The first Keyblades were crafted in the image of the χ-blade, both by those who wanted the light of Kingdom Hearts for themselves and by those who opposed them. Sora, the series' main protagonist, wields one on his journey across the worlds, and Birth by Sleep lets its wielders travel between worlds on a Keyblade glider.