In the game, you didn't destroy the world during the apocalypse. You protected your bit of it, and now, as a fallen angel, dragon, ancient god or demon, you're the ruler of your part.
If the setting is broadly contemporary, then the fact that characters are witches does not disqualify it as a game with a modern environment.
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Instead of destroying the world, you are protecting your part of it from the Apocalypse beyond your borders. You are the ruler of a safe-haven.