User blog comment:B214/Question and Answers 6/@comment-207.96.205.3-20160828100006/@comment-9595671-20160828102739

Azi Dahaka I believe knows numerous magic spells, such as the power to seal magicians' magic abilities and cast multiple forbidden spells at the same time. This includes free usage of space and time magic.

Crom on the other hand? He's just crazy strong and simply managed to gain the ability to survive a weapon that is deadly to evil dragons by training alone. Keep in mind the Holy Grail didn't enhance him like all the other Evil Dragons too.