Around 1165, a council was called in Polonnaruwa to discuss the reform of the sangha. Parākramabāhu's chief agent in the enterprise was to be the Mahathera Kassapa, an experienced monk who "knew the Tipiṭaka and was exceedingly well versed in the Vinaya". There was immense resistance to Parākramabāhu's efforts, in particular from the Abhayagiri sect who now adhered to the Vetullavada tradition, who the king found to be particularly corrupt. Many monks moved abroad rather than participate in the reforms, whilst others simply abandoned the cloth and returned to lay life. In this they may well have been encouraged by Parākramabāhu, who seems to have felt that the "purification" of the priestly orders depended as much on the expulsion and exclusion of the corrupt as it did on the rewarding and encouragement of the orthodox. There are several references to individuals being given "lucrative positions" in order to keep them out of their respective Orders. Finally, the king summoned the leaders of the sangha on the island once a year, centering the visit on a ritual on the banks of the Mahaweli river—possibly a practical means of keeping up-to-date with their progress and their standards.