Tiangou

In legend Tiangou appears in narratives connected with Houyi and Chang'e: after Chang'e consumed an elixir of immortality, a black dog that had licked the remains of the pill grew large, chased Chang'e, and swallowed the Moon (and Chang'e). The Queen Mother of the West captured the dog, assigned it a heavenly office and the title Tiangou; the dog then spat the Moon and Chang'e back out. Separate traditions treat the name also as an asterism and as a guardian spirit in astrological contexts.

As a malign figure Tiangou is described as resembling a black dog or like a meteor; sources explicitly call it a black dog that eats the Moon. As a benevolent spirit some accounts describe it with the appearance of a white-headed fox. In astronomical-literary usage Tiangou is also the name of an asterism (an identified star-group) found in ancient Chinese sky-mapping, located in the region corresponding to Argo Navis in those sources.

Tiangou is chiefly described as the creature that 'eats' the Sun or Moon during eclipses and thus functions in myth as an explanation for lunar (and sometimes solar) disappearance. In narrative form it can swallow the Moon (and the lunar figure Chang'e) and later expel them when captured or assigned celestial duty. In astrological/astronomical usage Tiangou functions as a named asterism and is called a 'constellation guardian of welfare,' a protective or marking role in traditional celestial mapping. Iconographically and mythically Tiangou is opposed by protective figures such as the deity Zhang Xian, who is depicted aiming at the sky to drive the beast off and protect children.