This discussion reopens the file on Plethon’s purported stay in Ottoman territory in order to trace the origins of the Plethonean belief in sectarianism as a vehicle for attaining Utopian sociopolitical ends. In the first part, possible approaches to Plethon’s alleged study with the mysterious mentor Elissaios are considered. In the second part, an argument is presented that in both the changing Ottoman Empire and the disintegrating Byzantine Empire esoteric societies contemporaneously developed a potentially antinomian role. Just like Plethon’s ‘brothers’, the ‘Brethren of Purity’ of al-Bistami, Sheikh Bedreddin and Börklüce Mustafa opted for sectarianism in order to recover a supraconfessional religious law and construe a novel political identity. This indicates the probability of a common nexus between Rumelia, the Peloponnese and the Aegean spanning confessional lines and utilizing sect as the vehicle of utopianism.