The recipe for the Spirit Fusion Pill was also a prize for winning the Receptarier tournament. Which Xiao Yan won, and in turn aquired the recipe.
Queen Medusa gave Xiao Yan 1 year to become a 6th rank Receptarier, so that he could successfully create the pill. Since there are no known current users of the spirit fusion Pill I cannot supply you with too much information about this pill, but since it was requested I did my best.
Hope I helped!