Originally posted by Luminous Dark:

I just looked it up on the wiki. Apparently they begin spawning in the meadows at night after you've defeated Eikthyr. I guess if I want peace, the next time I start a new game, I'll just not defeat Eikthyr. I wonder if they'll still spawn if I defeat the other bosses but not Eikthyr

You could basically defeat yagluth before any other boss, however that will spawn in fulings at night in the meadows. Just make sure you have a bit of a base setup before you start killing bosses.