Franz Bonaparta is considered to be the one responsible for the eugenics experiment that led to the birth of the Liebert twins and is also attributed as the author of the storybooks used to indoctrinate the children of Rose Mansion. Most notable of them was The Nameless Monster, from which Johan took both his name and his mode of operation. Other famous books of his included The Big Eyed Man and the Big Mouthed Man, The God of Peace, and The Quiet Village. His storybooks deal very heavily in metaphor and symbolism, often with monsters as important characters in them. Most also deal with the idea that human nature contains the ability to become good or evil, though his works tend to denounce humanity rather than uplift it.
He repents for all his actions after witnessing the death of Grimmer, he confronts Johan with the intention of killing him but he is in turn killed by Roberto before he can go through with it. While his real name is Klaus Poppe, other names that he has used include Emil Scherbe and Jakov Vyrobek.