User blog comment:Nomad27/What was the Black Scripture's goal in using Downfall of Castle & Country?/@comment-11990868-20150912025740/@comment-26836039-20150912052248

So they wanted to retaliate after finding that a strange sorcerer wiped out the Sunlight Scriptures and then perhaps they're investigating Ainz' whereabouts. They brought the miko and the WCI as an insurance if the enemy is far too strong for them to beat and control that enemy as an ally. This is great. It's very plausible.

Edit: @LordDarmo - this is most likely the scenario when you combine the above speculation + CDL.