[Darkstone]

Actually, this wasn't caused by someone else.

You should read section (VII - Dominion) of your manual. The part of how you died should be made clear in the last part of that section.

So to prevent that sort of thing, either take a strong dominion (7+), prioritize building temples, or start preaching with your prophet early on. Or if you're a blood nation, you can also start sacrificing blood slaves in your temples.