The carving of gemstones for personal adornment and for use as seals for documents is an ancient art form that was continued throughout the history of the Byzantine empire. This oval agate stone is carved in the intaglio technique, with its figural design and Greek inscriptions hollowed out of the stone surface. The saint's identifying label on the stone's obverse, naming him as Saint Theodore Teron "the military recruit," and the prayer on behalf of the gem's owner on the reverse, are executed in retrograde (reverse) script, confirming that the gemstone would have been used to make a positive impression in wax or a similar material. The figural decoration on the gemstone's obverse depicts a contest between a multiheaded dragon and the armed military saint Theodore Teron, the third-century Roman soldier from the Pontos region (on the southern shores of the Black Sea) martyred for his Christian faith under the Roman emperor Maximian (r. 286–305, 306–8).
The style and iconography of this private work of art, which would have functioned both as a miniature icon and as a personal seal, suggest classical inspiration. The saint's realistic body proportions, balanced stance, and vigorous activity resemble those of classicizing figures popular in the Late Byzantine period. The dragon with its multiple heads—seven or eight, plus the end of the tail—is rare in Byzantine iconography and seems to recall classical images of Herakles slaying the Hydra. Late Byzantine comparisons between military saints and the Greek hero Herakles are attested, as in the epigram for an icon composed by Manuel Philes (ca. 1275–ca. 1345), the renowned court poet of Constantinople. This representation of one of the most popular military saints of the Late Byzantine period illustrates the continuity of Theodore's cult into the empire's final centuries, as well as the ongoing popularity of classicizing styles and ancient art forms in the period.