Meng Qiu

He betrayed the Soul World and helped the Upper Realm to create a sacrificial array. The reason for doing so was because the Spirit Tree stopped speaking to him and he became resentful (Spirit Tree thought he no needed its guidance). He was killed when the spell he put on the Spirit Tree was broken by Blood Velvet and Jun Wu Xie.

Background
Meng Qiu, the strongest spirit envoy in the Soul World of all time, was created by the Spirit Tree in the early years when the Soul World was established. It could be said that he was one of the oldest spirit envoys created by the Spirit Tree. He had no predecessor to guide him, and could only nesciently figure the connotation of his existence all by himself. Since he had been serving beside the Spirit Tree for many years, everyone would often think of him as the very first guardian of the Spirit Tree.