User blog comment:B214/Light Novel Volume 16 spoilers/@comment-1392308-20131019074749/@comment-1359322-20131019083555

Why not? 666 vs Team DxD seems like a very good battle. Come to think of it could the reason why the God from the Bible create the Sacred Gear system is because he wants to use the humans to battle 666. Well Rizevim is a monster himself, also the Evil Dragons seems very powerful too. So Issei getting more power-up isn't that bad. Hey Issei lost to Euclid too, he only managed to hold back Euclid.