User blog comment:B214/Volume 23 discussion blog/@comment-172.58.16.1-20170324223136/@comment-31137559-20170325001737

If they have been banned then what makes you think they'll let Issei use one. If you are way too powerful and take a king piece, you could die. For example, someone like Sirzechs could never use a king piece. And the evil pieces were created to reincarnate other species into devils and give devils an enhancement of certain stats. While the king piece was mainly used for the strengthening of power. Issei having the power of Infinity and the power of Great Red and having a king piece on top of that, Issei would die.