玄武

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.

玄武门之变 (Xuanwu Gate Incident, 626 CE) was the palace coup where Li Shimin ambushed and killed his brothers at Chang'an's Xuanwu Gate, forcing his father to abdicate and becoming Emperor Taizong of Tang - one of the most consequential coups in Chinese history.