Board Thread:Episode Discussion/@comment-23712247-20160203074906/@comment-27820084-20160225210540

That...makes a rather nice amount of sense. But I think that humans made a form of living dust creature, but humanity, in its greed and stupidity, tried to use the living dust but corrupted it (Dragon Age style). The basis for this type of dust came from mini pieces of the moon. This corrupted dust would turn into the Grimm and start attacking its creators, the humans.