The western king cobra was a vicious creature so letting it live would do more harm than good.
Lin Jin just happened to feel like trying out the edict amulet spells he learned from the old Taoist, Wu Qian. There were many variants of edict amulets and their methods of use were extraordinary. But in a nutshell, it revolved around the five elements.
Among them was a most amazing Divine Mountain Amulet used to subjugate monsters.
Lin Jin had researched this amulet before and this seemed like a good time to test out the amulet's powers.
At this thought, Lin Jin took out a Divine Mountain Amulet that he practiced writing out previously. Invoking it with the Dharma body, he tossed it at the king cobra.
"Mountain formation!"