User blog comment:B214/Volume 21 info & spoilers/@comment-73.160.58.215-20160327154610/@comment-27232228-20160327215121

I see. Many thanks for correcting. Gonna need to expand my own reading then :D.

Also, after reading the Carmilla novella in Gutenberg, the Karnstein name makes sense, nah, it is basically what Ishibumi meant from the start, especially after relating the novella's story with Dracula (guess the Carmilla and Tepes faction reflect these two vampire stories because they form the basis of most modern vampire works). I guess we just misread カ as ガ and many people stuck with that.

As for the Malebranche appearing in Slash/Dog, there's that possibility but it's less likely since in the last chapter mentioned the Wizards of Oz as well as the issues regarding the Five Noble Families of Japan, and they are more tied to the Underworld's side of things (Guess they too have a grudge against the Old Families and wanted to re-ignite the Devil Civil War).

As for the villains of the next arc, rumors (and in the Japanese wiki article for DxD) abound that Sakra is making his move. So we have a good possibility that the Hindu God will become a main villain along with the Twelve Demons of Malebolge (the format is very much similar like Hades and the Hero Faction in the third arc).