During the reign of the Great King Ahlsendar, the Guild of Writers and Healers were working on a plague, in order to be used as a biological weapon in case of eventual emergency. That plague eventually destroyed the Pento.
When Ahlsendar's Plague turned against the D'ni, the Healers and the Guild of Chemists were working hard to find a cure. King Behnashiren was of no help and in some of his speeches he accuses the Guilds of "shallow efforts" and "failing their own people." When the Lost Books of Birenni were found, Jaysem led the Guild and eventually he declared the cure of the plague in 2268.
In 5312 disease broke out in Nehw'eril District most likely originating from Yasafe. The illness was not nearly as lethal and the Guild reacted extraordinarily fast in finding a cure. According to a story, King Me'emen expelled some of the previous Healers due to inactivity, and appointed as Grand Master the Healer who found the cure.