After re-reading Oathbringer I realized that we never actually see a spren bonded to Szeth (maybe I just missed it but I'm pretty sure). Szeth also swears the third ideal thus becoming a full knight radiant, but he doesn't use a shardblade, rather he uses nightblood instead. I'm just wondering if I missed something, because it seems that Szeth has bonded night blood, and somehow gotten skybreaker abilities. Does anybody know why this is?