Fryderyk Żyskar (alias Jozafat), priest of the diocese of Mogilev, known and respected before the First World War as the pastor of many Catholic parishes in the vast expanses of Russia, prisoner of conscience, exile, historian and diarist, is today an almost forgotten figure. This text looks more closely at the figure of the above-mentioned priest and discusses the surviving materials of Fr. Fryderyk Żyskar, held in the AGAD and the Library of the Catholic University of Lublin.