Taotie

Pronounced "TAH-oh-TEE-eh." It is a creature represented in Chinese art by a stylized face of some dragon-like or dog-like monster. Its real appearance is a composition of loops, changing colors from yellow to red, sliding over surfaces, sometimes composing themselves into a face-like arrangement, just before it leaps off the surface to attack. It haunts mirrors. The taotie is a beneficent monster, guarding our world against the Mirror People. At the end of the Mirror War, Huangdi either conjured up the taotie or was given it by an unknown party, to guard the borders between us and the realm of the Mirror People by guarding mirrors. It doesn't just attack Mirror People; it attacks anyone who appears to be making magical attacks through mirrors. The people it attacks usually just vanish. It is powerful enough that some classes of glamour-using vampires are afraid to cast reflections, for fear of it.