Patriarch Nicholas, who was born in the Italian Peninsula, had become a friend of the Patriarch Photios.
He had fallen into disfavor after Photios' dismissal in 886 and retired to a monastery.
Emperor Leo VI the Wise had retrieved him from the monastery and made him mystikos, a dignity designating either the imperial secretary or a judicial official.
Nicholas had been appointed patriarch on March 1, 901.
Emperor Leo, because of his anxiety for a male heir, has married three times, thus incurring the censure of the Greek church, which normally forbids a widower to remarry more than once.
When his mistress, Zoë Carbonopsina, presents the emperor with a son, Constantine, in 905, he makes her his fourth wife after Constantine's birth, against the bitter opposition of the patriarch Nicholas Mysticus.
Although he reluctantly baptizes the fruit of this relationship, the future Constantine VII, Nicholas forbids the emperor from entering the church.