User blog comment:B214/Volume 22 spoilers/@comment-86.153.130.29-20161022030610

The mian reason I don't think Elmenhilde would be Issei's Rook is that Rooks role in the team is to charge the front lines like a Tank or provide long range cover fire. The stealth, reconnaissance and the abillity to confuse people with fog and shadow would need speed. The Pawn would provide more use to a Vampire then the slow moving Rook.