A Novel That Starts with Watching the Fall of the Sword God

A low-level co-worker went to a snowy mountain to save his sick mother, and was involved in a deadly battle between the six-door god hunter and the demon sect's king. With his extreme calmness, he witnessed the god hunter being plotted by his colleagues, and the king died in battle. The protagonist accidentally fused with the evil bones of the demon sect and cured his mother...