Kyuubi

Another name for the nine tailed fox. The demon is currently sealed inside of Naruto, at times it will lend its chakra so that Naruto and it won't die in battle. His name is more of a title being derived from the words kyu meaning nine and bijuu meaning tailed beast. Kyuubi is the 9th tailed beast of the Bijuu and his  seal holder is Naruto. Since Naruto is a host he is called a jinchuriki. Kyuubi is probably based off of the Kitsune of Japanese Mythology.