Mission to the Peoples of Siberia
The defining work of Philotheos's episcopate was the mission to the non-Christian peoples of Siberia. According to the OCA life, his missionary activity was directed chiefly toward the Ostyaks, Voguls, and other Siberian peoples, and over the course of his ministry he is said to have baptized a very great number of converts. Missions were sent into distant regions, including expeditions associated with Kamchatka and the Berezovsky territory, and the work is described as reaching toward the far northern peoples.
Alongside preaching, Philotheos pursued the building of churches and the founding of schools as instruments of the mission. Sources record a substantial multiplication of churches and monasteries during his administration and the establishment of schools for the instruction of both clergy and the indigenous converts, among them schools founded in the Ob North. Even in his later years, by tradition, the aged schemamonk Theodore continued to travel into the northern territories to visit those he had baptized.