A Death Note is a supernatural notebook used by Shinigamis to kill humans, so they can extend their lifespans.
Powers and Stats
Origin: Death Note
Powers and Abilities: Death Manipulation (The Death Note can kill people who have their name written in it), Limited Fate Manipulation (Can control when and how people die), Limited Disease Manipulation (Can develop any specified disease into the victim if given the right time of death for it to progress)
Range: Low Multiversal (Can kill humans on Earth from the separate Shinigami Realm)
Weaknesses: The wielder must know the victims' name and face, the Death Note cannot make the victim do the impossible, it cannot kill a shinigami and is only known to work on humans.
Note: A full list of the rules of the Death Note can be found here.