... you are a god, existing on a plane of deity. Beneath you is a plane of existence where your potential followers reside. On your plane of deity you are not alone, there are other deities competing for followers on the plane of existence. Both planes have a geographic presence and your goal is to dominate on both of them. The resource is followers, but they only exist on the plane of existence. But as they die, they transfer to the plane of deity and depending on their beliefs, become a resource of their respective god.

So for example if you as a god are challenged on the plane of deities, it is in your interest to send your believers on the plane of existence into some hopeless conflict where they die and join you on your plane. As the believers exist on your plane of deities they have a, let's call it, re-incarnation timer that when expires sends them back to the plane of existence, most likely as believers of you.

I think this mechanic will create an interesting fluctuation of resources that, as far as I know, doesn't exist in any RTS as of yet.

And btw I am super drunk as of writing this, so bear with me.