The Black Tortoise, a mythological figure often depicted as a tortoise intertwined with a snake; it represents the north, the element of water, and is worshiped in Daoism as a guardian deity (also known as 真武 zhēn​wǔ)

door; gate; gateway; doorway; opening

Connects a describing word or phrase to the noun it describes, similar to 的 de but used in formal or literary writing.

a sudden or major event; a rebellion; a disturbance or emergency