I've always Wondered why no one makes Stories about: Anime Overlord x Warhammer fantasy battle. This is a gold mine for Stories. If I knew English well, and could write in it, I would write.
If there are such experts in both of these universes, why don't you write? I and many others will support you.
You can start with the fact that Nazarick does not enter the New World. And here comes the ever-howling World of war. Unlike the new world, the world of Warhammer fantasy Battle will have many strong and smart opponents. Which can make the inhabitants of Nazarick sweat. I personally think that you can make a very good story out of this.