|Information important to every Death Note can be found on Death Note (object). A complete list of rules of how to use a Death Note can be found on Rules of the Death Note.|
Ryuk's Death Note is similar in appearance to Sidoh's Death Note, having a black cover with the words "DEATH NOTE" written on it.
When he first meets Light Yagami, Ryuk warns him that when it is Light's time to die, Ryuk will write his name in his own Death Note.
When Light is about to die, he begs Ryuk to write the names of the Japanese Task Force and SPK members in his Death Note. In the manga, Ryuk agrees to write down a name and pulls out his Death Note, but unimpressed with Light's "pathetic" display, he writes down Light's name instead.
In the anime, Light escapes the Yellow Box Warehouse when Ryuk reminds him that he is not on anyone's side. He is unwilling to remain attached to Light while he serves a lifelong prison sentence, and he writes Light's name in his Death Note while remarking on the interesting times the two have had together.