I dunno if you guys noticed, but the demons speak as if all this has happened before. It's strange, isn't it? Perhaps because they are demons, extradimensional and/or supernatural beings, these guys are aware of the regression, the changes in the timeline? It does explain why Leviathan spread the plauge of the Red Death in the forest, since there is a demon in the Morgue clan. Typical of demons to be so manipulative, yet it is so very effective.