The most imposing creation of Russian icon painting, the iconostasis, was a wall of permanently fixed icons separating the sanctuary from the congregational areas of the church. The iconostasis can be understood as a window upon Heaven that makes visible the cosmic order and the many forms of God’s self-revelation. Smaller, portable iconostases, such as this one, began to appear in the second half of the 16thcentury, borrowing their arrangement from the church models. In this example, the tallest and most impressive register is the first tier, called the Deesis tier, in which full-length figures—here including Mary, John the Baptist, archangels Gabriel and Michael, and apostles Peter and Paul—bend in prayer towards the enthroned Christ. Directly above is the feast cycle, showing imagery connected to various recurring religious celebrations. The third tier is devoted to the prophets arranged around the Mother of God, and in the fourth, the Bible’s patriarchs turn towards the central figure of God as Lord of Hosts. These portable church-like devices may have been used for worship during travel or by soldiers during military campaigns, but they were principally instruments of private devotion. Scholars have linked the development of portable iconostases to the privatization of devotion that took place as Orthodoxy responded to the Protestant Reformation (1517–1648).