User blog comment:B214/Volume 22 spoilers/@comment-104.230.254.245-20160819121246/@comment-9595671-20160819171633

And the reason why it was Beelzebub out of them that was not? He made the Evil PIeces and his and Grigori's technology helped make the Brave Saints, so he was required to stay. Plus he and Sirzechs were the strongest of the Satans as well.

Not sure why Gabriel was chosen to stay behind out of the Great Seraph though, does anyone know the reason for that?