There are in total 14 Shinigami in death note. Though only Ryuk, Rem and Sidoh seem to appear in the series. Shinigami are Japanese death gods. By using there Death Notes to kill humans they gain more years to there own lifespans. It is not necessary for Shinigami to eat, drink or sleep, so for Ryuk this is just a luxury. When a Shinigami's Death Note happens to fall into the human world and a human picks it up the Shinigami responsible for the lost Death Note must stay with the human until the human dies. When the human dies the Death Notes ownership returns to the Shinigami it came from. There are many rules that come with the ownership of a Death Note. From the complex to the downright simple. The human who uses the Death Note can neither go to heaven nor hell.