Before leaving, Yang Qing left the sect master of the Spring Rain Sword Sect with a couple of hundred pearls that he had imbued with pure yang qi which sect master Mu Gen could use to help some of his members endure the frigid cold qi surrounding them better. The pearls could benefit even the sect master himself.
The purity of the yang qi was in respect to Yang Qing's present state. Even before the slight developments made to his physique, both his yin and yang qi were pure enough to rival naturally formed treasures based on those energies, and with the recent developments, that purity had grown.