Not all swords.

(At least he answers a little more directly now. )

When an object reaches a hundred years, it gains a soul and becomes aware. That spirit stays with it and if it becomes strong enough, can perform certain deeds like refusing to cut or cutting particularly well. It all depends on how the object is treated.

And then there are special humans who can call upon that spirit and grant it a physical form so that it can act on its own will.