Enkolpion were small pendants worn around the neck, and examples have been found tracing back to Late Antiquity. The cross shape was the most popular symbol for such amulets, as the silhouette was believed to have apotropaic qualities. Many enkolpion were designed to hold reliquaries, as can be seen here by the opening function of the pendant. The reliquary was believed to work in tandem with the talismanic qualities of the cross-shape to protect the wearer from harm and evil. Such pieces were very popular in Byzantium, and were made in an assortment of materials, from gold and silver, to bronze and lead.
To disocver more about Byzantine art, please visit our relevant blog post: The Byzantine Empire, Art and Christianity.