Epanagoge
The Epanagoge (, "return to the point"), more properly the Eisagoge (, "Introduction [to the law]") is a Byzantine law book promulgated in 886. Begun under Basil I the Macedonian (r. 867–886), it was only completed under his son and successor, Leo VI the Wise (r. 886–912). As its name suggests, it was meant to be an introduction to the legislation of the "Basilika", published later during Leo's reign. The work, organized in 40 volumes, covers almost all spheres of law, and was explicitly meant to replace the earlier "Ecloga", dating to the iconoclast Isaurian dynasty. Nevertheless, it draws some  inspiration from the "Ecloga"; the main source, however, is the "Corpus Juris Civilis" of Justinian I (r. 527–565), albeit often heavily altered. Patriarch Photius of Constantinople worked on its compilation, and wrote the preface and the two sections dealing with the position and powers of the Byzantine emperor and the patriarch; notably, the powers of the patriarch appear broader than in Justinian's legislation, both with regards to the emperor and towards the other patriarchates of the Pentarchy. The "Epanagoge" was withdrawn from official use soon after its publication, being replaced by the "Prochiron" (which was earlier considered an antecessor  of the "Epanagoge") twenty years later, but served as the basis for several private law books, such as the "Epanagoge Aucta" or the "Syntagma Canonum". Through its translation into Slavonic, the "Epanagoge" found its way into Russian canon law, including the 13th-century "Kormchaya Kniga". Its provisions on the patriarch's and church's position vis-a-vis the temporal ruler played a great role in the controversy around Patriarch Nikon in the 17th century.