Hollows are... Corrupted human souls are the easiest way to put it. They're invisible to those who aren't souls or can sense spiritual energy, and they prey on other souls, absorbing or corrupting them in turn. My job is to cleanse them, so that they can either continue on to the Spirit Realm, or be dragged down to Hell.

A homunculus? I know one of those. Except she wasn't made by 'alchemy', and she has the same powers that I do... And then some. She's also rather robotic in her mannerisms.