Zhou Xue is a sword that saved the world.
Zhou Xue: "Standing here, first of all I want to thank my boss Yun Ji. Without him, I would still be a wisp of energy floating around in Kunlun Mountain. He gave me another life, even though he is too dead now. Let us miss him together, the first brother of Kunlun Mountain - Yun Ji..."
Things should have developed as mentioned above.