玄武 (Black Tortoise) is one of the Four Symbols
四象 of Chinese astronomy — Azure Dragon
青龙 (east), White Tiger
白虎 (west), Vermilion Bird
朱雀 (south), and Black Tortoise
玄武 (north). Depicted as a tortoise entwined with a snake. Later worshipped in Daoism as
真武大帝. The Qing emperor Kangxi's taboo name
玄烨 led to the character
玄 sometimes being written
元.