From the Treasury of Daily Prayer:

St. Matthias is one of the lesser-known apostles. According to the Early Church Fathers, Matthias was one of the seventy-two sent out by Jesus in Luke 10:1-20. After the ascension, Matthias was chosen by lot to fill the vacancy in the Twelve resulting from the death of Judas Iscariot (Acts 1:16-25). Early Church tradition places Matthias in a number of locations. Some historians suggest that he went to Ethiopia; others place him in Armenia, the first nation to adopt Christianity as a national religion. Martyred for his faith, Matthias may well have met his death at Colchis in Asia Minor, around AD 50. The Church of St. Matthias at Trier, Germany, claims the honor of being the final burial site for Matthias, the only one of the Twelve to be buried in Europe north of the Alps.