Three main categories of bronze artifacts exist: ritual vessels, luxury items and sometimes placed in tombs and weapons. Production quality peaked in the late Shang (B.C. 1600~B.C.1100) period. One characteristic form was the Jue, a ritual vessel standing on three legs, apparently intended for the warming of wine. The surfaces of most ritual vessels were commonly covered with stylized surface decoration.The most common motif was a mythical creature lacking a lower jaw known as the taotie mask. Many vessels carried inscriptions indicating why they had been cast and explaining their intended use.