What exactly is Azazel after in all this? I know he is constantly spouting peace, but somehow that doesn't seem like the end game of a super being. I wonder if he is trying to bring back "God from the Bible"? I get this from him allowing Cao Cao to return, he wants the spear, it contains God's Will. He has 2/3 of the Holy Grail, with the power of resurrection, conveniently split into 3 bowls to resurrect the trinity. He would then need the incinerate anthem containg the holy cross. Perform some kind of supernatural/scientific mumbo jumbo and viola! One re-incarnated "God of the Bible" brand spankin' new and Azazel gets his long sought after forgiveness.
If the 3 of them wouldn't supply enough power, then that is where 666 comes in. If Azazel actually wanted to sacrifice 666 or cause a battle between Great Red and 666 to release the energy of both dragons during mutual annialation.
Could turn out that this was some sort of a back-up plan and the reason sacred gears and 666 were created in the first place and why Azazel et al are so focused on sacred gears.
Of course this is all just thoughts that have probably already been discounted in a spoiler I haven't read and they could be crazy off the mark. I'm just wondering what Azazel is really steering them all to?