The dog that eats the moon during an eclipse is Tiangou, the “Heavenly Dog.”
In Chinese mythology, Tiangou is commonly portrayed as a black dog or, in some traditions, a meteor-like celestial being. Its appearance was used to explain eclipses: the creature attacks and swallows the Moon, causing darkness in the sky. Some versions also say it can consume the Sun.
One legend connects Tiangou with Houyi and Chang’e. After Chang’e took an immortality pill and fled to the Moon, Houyi’s black dog followed her, grew enormous, and ate both the Moon and Chang’e. The Queen Mother of the West eventually captured the animal, made it spit them out, and appointed it guardian of Heaven’s gates.
Tiangou should not be confused with Japan’s tengu. Despite similar-sounding names and shared Chinese characters in some discussions, the tengu is generally a birdlike or long-nosed supernatural being, whereas Tiangou is the eclipse-associated dog.