In Deltarune Papyrus (Sans's brother) is surprisingly absent in chapters 1 & 2. What if Papyrus was the knight? Sans says specifically "He needs friends" and if you create dark worlds, you could create friends out of physical objects. My other theory is the last dark world ever created was inside of mount ebbot and Kris was the one who started the war between humans and monsters after the ROARING was killed.
