The monster of the day worships the day, while the creature of the night rules the night. But nothing could be more opposed to both than to live on the same land at the same time.
Humanity prospered until it entered the pre-industrial age, when the largest cities saw the first long chimneys made of brick, while smaller villages still had to cut logs from the forest with an axe.
But to get to this heyday, something had to be sacrificed.