User blog comment:B214/Volume 23 discussion blog/@comment-172.58.20.164-20170406005107/@comment-30924344-20170406013100

Azazel is the most important character in the series, because without him, there would be no story for Slash/Dog and also DxD. Azazel is the one who instigated both stories. For Slash/Dog he was woring behind the scenes since Tobio was a boy to observe him and thanks to that, Azazel could send Natsume to save Tobio. For DxD, similarily to Tobio, Issei was observed by Azazel (difference is he only did it when Issei became his age) and that is why he sent Raynare to observe him and if that didn't happen, no reincarnation.