As is always with artifacts of power, stories arise around them to explain their origins. The keyblades are no different. Some scholars hold that the weapons, always bearing at least the semblance of a key shape, were given to us so that we could unlock a great treasure behind 'The Door to the World'. Those more military minded believe that the keyblades are weapons bestowed upon the worthy, ordaining them as knights of a bygone code. And those who would call themselves religious say that these keys are ways to unlock the door to Heaven, so that the Maker may come down and anoint the land in His divine light.
Whatever the truth behind these weapons, their origins, their purpose, their effect upon the world, and upon humanity, is well documented. Keyblade bearers, tested by the foremost scientists of every generation, were found to be more durable, faster, and stronger than those without. Rumors have even abounded that a keyblade wielder perceives the world faster than reality, and that they could react quickly enough to catch bullets. While those are simply unsubstantiated rumors, either fact and hidden behind a gag order or mere deification of these chosen few, it is truth that keyblade bearers are superhuman.
One of the most interesting aspects of the keyblade is what becomes of it when a bearer dies. Should the wielder die without keyblade in hand, it is assumed that the blade vanishes forever. Should they wield it, though, the blade falls with them, embedding itself always blade down in whatever spot its master died in. Ages may past, and the keyblade of the fallen will lose no luster, never rust or fade. They become permanent fixtures of the land, unable to be moved, even with the heaviest of equipment. Eternal tombstones.