The Tatsu are the serpentine elemental and celestial dragons of the Far East which originated in Chinese mythology (Long) and spread to Korean (Yong), Vietnamese (Rồng), and Japanese (Tatsu) mythology. Whom were first used in 2005 by Chaosium as a fictional race for the Call of Cthulhu RPG.
The Tatsu are a race of dragons, elemental beings whom possess incredible powers over nature. There are two earthly types of dragons, the kazu-tsuchi whom have an affinity with the element of fire and the wata-tsumi who have an affinity with the element of water. The kazu-tsuchi live deep below the earth and when awake, their playing in the molten rivers causes earthquakes. It can breathe a flames or spit lava, and cause volanic eruptions or earthquakes. The wata-tsumi in turn live in bodies of water, and control the rains. It can breathe a torrent of water and call forth tsunamis. The heavenly dragons live in the Palace of the Green Dragon. It breathes blasts of wind or shoots lightining bolts, and their aerobatics cause thunder and typhoons. They feed from their element (e.g. moisture, flame, etc).
They regenerate by siphoning Chi from their element and are able to communicae with humans via telepathy, projecting images. Dragons can also summon and consult with Mythos entities. Fire dragons usually call upon Cthugha or Tulzscha, water dragons contact Yig or Cthulhu, and heavenly dragons consult Nyarlathotep or Hastur. The water dragons use bodies of water, fire dragons will visit volcanoes or fires, and heavenly dragons will use electricity, Chi, and spirit. Dragons are the personification of Earth's life force, Gaia's living will. They are Earth's natural defense system, basically the bio-system's white blood cells which attacks non-terrestrial invaders.
Due to the human race, the Earth is slowly being killed by their overexploitation of its natural resources and the pollution they've generated. Which has kept dragons in a deep slumber and caused the some of them to disappear. It's in the Dreamlands, where the most active dragons are located. On Earth, their lairs are known as "dragon paths" (ley lines), with the dragon's lifeforce within the energy lines crisscrossing the planet.