The Sentinels no business but gold

"That they do from the fall to winter equinox. It's the darkest time of the year and, since they no longer can enjoy sunlight, it is more comfortable for them to travel that way," Wraen explained. When you looked closely at most myths and traditions there were only few that you could not find any real life explanation for of, why were they there. In this case - when the weather grew cold and lands became barren, when the Death reaped so many souls, who had either not survived the freezing temperatures or succumbed to famine - it made sense that alongside their master the dead walked the Earth too. 

"But this is true only if you believe in it. If you do not - then it is just a fancy story," she said. "It applies to all supernatural beings. Magic too."