Heidi (god)

Heidi (Black Emperor) is a deity in Chinese religion, one of the five manifestations of Shangdi. He is associated with water and winter. His animal form is the Black Dragon and his stellar animal is the tortoise-snake. 
Taoist myths involving the Black Emperor.
A Taoist title of the Black Emperor is the "Dark (or Mysterious) Heavenly Highest Deity" (). According to a myth, during the fall of the Shang the Demon King ravaged the world, so that Yuanshi Tianzun ordered the Jade Emperor to appoint Heidi as the commander of twelve heavenly legions to fight this evil. Heidi defeated the Demon King and was subsequently granted the title of Mysterious Heavenly Highest Deity. In temples dedicated to him, he has a bronze tortoise and serpent under his feet. This means that the good always prevails over evil.