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)

(bound form) physical matter; substance; the material essence of an object

molten rock that flows from a volcano or fissure in the earth; the rock formed when this material cools and solidifies