User blog comment:B214/Volume 22 spoilers/@comment-27083298-20161112215056/@comment-10330822-20161113153128

Possibly, but it seems more fitting for it to be Crom, given the name play alone. Think about it, Mr. Black is considered to be x8 Pawn pieces, the same as Issei, meaning he could be Heavenly Dragon, Satan, to God-level giving the rules of WRC. The idea that its just some random new character Rias's group came across seems kind of off. Besides, Crom and Issei still haven't gotten that full on bout yet. Given how close Crom was getting with the group in v19 and 20, I wouldn't be surprised at all if it was him, and he joined in hopes of getting to face strong enemies, like Issei.