Seyyid İbrahim Bilal is reported to be a sayyid descended from the Prophet (through Husayn) who led volunteer fighters by sea for the conquest of Istanbul in the Umayyad period. Caught in a Black Sea storm, he took refuge in Sinop harbor but was martyred by the local Byzantine governor, remembered as 'the first martyr of Anatolia.' His tomb in the Ada quarter of Sinop, beside the mosque named after him, was built in 679/1280 by Emir Beklemiş per its inscription. (Sources: Sinop Governorship; Culture Portal; Sinop Theology Journal.)