User blog comment:15sok/How Would Issei Human Friends Feel About His Secret/@comment-6482575-20131217082255/@comment-1359322-20131218020459

There's a possibility that Ravel lost her right to get her own Evil Pieces the moment he become Riser's Bishop. At least Grayfia and Kuisha, who is of the correct age to get her own Evil Piece, doesn't have their own Evil Pieces.