Moros had searched for the human that his wife considered to be her sister and only found a way of contacting her. And that was a humble cultivator who had the network to pass a letter to her.
Later, he encountered a cultivator with lowest flow of Qi who claimed that he could pass the letter to the poison master directly with his ability.
During his search, he was told poison master who used to run the Duyi pharmacy has retired and nobody knows where she is wandering