The unpredictable deity.

Mercury (in Greek, Hermes) was the messenger of Olympus and patron of merchants, travelers, and thieves. Wearing winged sandals (talaria) and a winged cap (petasus), he traveled ceaselessly among the gods. He was quick and cunning enough to steal fifty of Apollo's cattle on the very day he was born, and to fashion a lyre from a tortoise shell. He was also the only god who passed freely between this world and the underworld (the psychopompos). Alchemists gave his name to the one metal that flows at room temperature -- the liquid metal that moves swiftly and changes shape -- calling it mercury. From the mid-17th century, English mercurial became an adjective meaning "changing as swiftly as quicksilver, volatile." In astrology, too, those born under the planet Mercury were thought to be clever but capricious.

Byeonhwamusang (變化無雙) means "without peer in transformation" -- to change in ways so varied as to be unpredictable. Sun Wukong (孫悟空) of Journey to the West possessed the seventy-two transformations (七十二變). He became a fly, a tree, a man. Yet however he transformed, he could never hide his tail -- even in change, the essence remains. The Book of Changes explains that the very character yi (易) means "change." The ceaseless turning of the sixty-four hexagrams is the essence of the cosmos, and it offers the paradox that the only thing that does not change is change itself. In the "Weak Points and Strong" chapter of Sun Tzu's Art of War, the line "the form of an army should resemble water (兵形象水) -- water has no fixed shape, and an army has no fixed posture" was the martial ideal of boundless changeability.