I'm looking for a novel and it could be from we novel where MC is from a time where mana dries up and he transmigrated to a time when it still exists.
I've read that before, but I dropped it coz' it's way too similar to every events in Tales of Demons and Gods.
Pretty sure that's what happened in The Nine Cauldrons, but I'm equally sure that it's a theme in far more than one story.