The Four Gods
Roughly based on four constellations in the Chinese zodiac, there are a number of different aspects and reasons why they are so popular. However, in each myth and story they all have a few things in common. For one, each of the four constellations have a specific animal, colour and direction. They are:
Suzaku - The Vermilion Bird of the South and is a representation of the summer season as well as Yin. In China it is called "Zhu Que." Contrary to popular belief the Vermilion (red) Bird is not a phoenix although it is commonly depicted as one in pictures; although this is probably because it also has red & orange feathers. The seven mansions it guards over are: chichiri (well), tamahome (ogre), nuriko (willow), hotohori (star), chiriko (net), tasuki (wings), and mitsukake (chariot).
Seiryuu - The Azure Dragon of the East and represents the Spring season as well as Yang. In China it is called "Qing Long" and is depicted as a sea-green dragon who is both fearsome but also benevolent to humans; as well as the representation of wood in the five elements. The seven mansions it guards over are: ami (neck), ashitare (tail), mi (basket), nakago (heart), soi (chamber) su (horn) and tomo (root).
Genbu - The Black Tortoise of the North and a representation of Winter. In China it is referred to as Xuanwu which literally means black tortoise and snake even though it is more commonly drawn as a snake wrapped around a turtle which is symbol for longevity. The seven mansions is guards over are: hatsui (room), hikitsu (dipper), inami (cow), namame (wall), tomite (emptiness), umiyame (roof), and uruki (woman).
Byakko - The White Tiger of the West and representation of Autumn. In China is called "Bai Hu" and represents strength especially when in a position of power. In legend it is said that a tiger's tail would turn white after it has reached it's 500th birthdate, thus making it a sort-of mythical creature. The seven mansions it guards over are: amefuri (net), ekie (stomach), kagasuki (investigator), subaru (resting place), tatarai (hill), tokaki (stride) and toroki (tutle snout).
The most common of all the myths involving these four gods is in a story about a legendary empress of China, Nu Kwa who had become a deity by crossing the heavens. While evil deities were waging war a pillar that holds up the heavens began to crumble and water pour onto the earth. In order to save it, Nu Kwa pulled stones from the night sky (each in representation colours of the four Gods) and put them in between the cracks in the pillar until it was straight again. In order for the pillar to not fall again she also created the four gods to protect it. She put Suzaku in the South corner, Seiryuu in the east, Genbu in the North and Byakko in the West.