So wild guess, but the goblet of water didn't react to Yuan's blood because he is not the Lord's descendant but is the reincarnation of the Lord who is also the leader of the demon sealing clan
The supreme lord has returned đđźđđź Yaun just be too nice in these last chapters. Love that he hasnt wasted anytime with dealing with these demons. Hes gonna end this battle pretty quickly, and hopefully grab their demon cores and eat all of them.