The five dragons recall the auspicious powers of the Emperor's majestic and benevolent rule. Groups of five dragons in fact suggest the "five blessing" of longevity, wealth, health, peaceful death and virtue, which according to the philosophical concept of the Mandate of Heaven, the ideal emperor possessed. According to this political and religious doctrine, implemented throughout the history of China, Heaven, embodiment of the natural order and will of the universe, only bestowed the right to rule to upright candidates. Five dragons also recall the five ever-changing elements of wood, fire, earth, metal and water. According to the "Five Actions" theory of Chinese cosmology, first mentioned in literature dating to the 4th century BC and perfected later during the Han dynasty, each element had its own characteristics and associations with different aspects of nature, such as a direction, a color or a season. The interaction between the five elements generated all things in the universe.