This is a terrific game!
The encroaching darkness as well as the gradual maxing out your tile upgrades adhere strongly to the theme, but what I really love about this game is the gradual reveal of its depth and the different strategies you might be able to use to win. Just when you think you've figured out, "OK, so I can also build cities for a research victory," you discover, "whoa, there's a potion factory?"