ideas for books

I know extremely little of warhammer40k, but someone going arround a city full of gods, worshiping gods that no one think exist and calling all other gods "heretics" just sounds way too funny

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I don't like the idea of mc beeing racist, so mc will probably be a reincarnator from earth that got a primarch's powers from rob. He will however have a skill that makes him deal extra damage to anything that is not a human

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I want mc to have "khorne dosen't care from what side the blood flows, only that it does" and "blood for the blood god, skulls for the skull throne" as chants for some magic(maybe summoning an army of space marines?)