I remember the Illithiad from when I was younger. It was one of my favorite source books. I might try to get another copy of it sometime so I can check it out again. It's been so many years since I've read it.
I guess the whole soul thing feels weird to me.
Gods in the setting get their power from the souls of their worshippers. Does the power just come from the living souls? Do those souls provide no more power after they die?
If the god loses all their living followers and thus becomes deprived of power... and potentially dies... what happens to all the previous followers who died and went to the god's domain area in the after life? Do they cease to exist with their god or go somewhere else?
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The thing that confuses me about the scorched earth thing is that I figured the dead three were getting their power from their followers also. Which I thought meant they would go down with the other gods.
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Maybe I'm overthinking the setting. I'm not sure how robust it's supposed to be under any kind of magnifying glass.