I don't think abandoning the city (and the traveler in the process) would be a good idea, what happens if the darkness destroys the traveler? Do guardians get to keep their abilities? Maybe, maybe not. It just seems too risky. And look at what happened to the fallen, they turned into mindless scavengers with no possibility of a future where they have a home of their own. In fact the fallen are facing extinction at the hands of everything (Including their own kind)