Qin Mu used a lot of time and effort to refine the poison. It was multi-composite, requiring him to refine it numerous times. He had to first make hundreds of basic poison pills, then use them to feed venomous creatures, for example, venomous worms, toads, and various insects. Once they were ready, he used them as fertilizer for poisonous mushrooms and grass.
He did it numerous times, until he managed to refine a couple poisonous eggs which he planted into the bone marrow of the two legs. Those poisonous eggs would not dissolve on their own, but when bone marrow began producing blood again, their shells would break, and the poison inside would flow into all parts of the body through the bloodstream, spoiling the person's divine treasures, breaking his primordial spirit, and wiping out his soul.