St. Methodius was a 9th-century Byzantine missionary and scholar, best known for his work in spreading Christianity among the Slavic peoples. Along with his brother, St. Cyril, he developed the Glagolitic alphabet, which was the first alphabet used to transcribe Old Church Slavonic, the liturgical language of the Slavs. Methodius served as the Archbishop of Moravia and played a crucial role in establishing the Christian faith in the region. His efforts helped to create a written tradition for the Slavic languages, promoting literacy and education among the Slavic communities. He is venerated as a saint in both the Eastern Orthodox and Roman Catholic churches.