Russian illustration 1820. of Saint Demetrios of Thessaloniki a Christian martyr of the early 4th century AD. During the Middle Ages. he came to be revered as one of the most important Orthodox military saints. Demetrios appeared in 1207 in the camp of Kaloyan of Bulgaria. piercing the pagan king with a lance and so killing him. This scene. known as the miracle of the destruction of tsar Kaloyan. became a popular element in the iconography of Saint Demetrios.