He was renowned for the rare austerity of his life. The Emperor Leo VI had married four times, and the Patriarch therefore forbade him entry to the church, and the priests who had married him were unfrocked. The Emperor cast the Patriarch out and drove him into a monastery. The delegates of the Roman Pontiff, Sergius III, gave their approval to the Emperor's fourth marriage, but, when the Emperor died, Nicolas was restored to the patriarchal throne and called a Council in 925, at which fourth marriages were in general forbidden to Christians. 'Mysticus' signifies the senior member of the imperial council. This saint was such at first, then a high-ranking courtier, but after this he forsook the vanity of the world and was tonsured. He died peacefully in 930.