The alchemy method requires one main ingredient as the guide, supplemented by various other materials.
This main ingredient is of utmost importance, as the efficacy of the elixir pills largely depends on it. Usually, the main ingredient is a pill pre-refined by the Pill Master with a unique technique, making it so that even if others learn the alchemy method, they cannot replicate the preparation of this main ingredient.
Although Zhang Yan does not possess a main ingredient, he can use the bottle of "Qi Blood Essence Pills" as a replacement.
One must understand that each Qi Blood Essence Pill contains the essence of at least a hundred Demon Cultivators. If an ordinary cultivator took it without a spell, they'd be overwhelmed and die from the sheer potency. Even a Blood Essence Sect disciple, if only at the Xuan Guang Realm, would need months to refine a single pill.
