Ryuk's Death Note

This Death Note is carried by Ryuk throughout the series. No other character touches or uses his notebook.

Appearance
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.

Plot
When he first meets Light Yagami, Ryuk warns him that when Light's time to die comes, 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.

In other media
Unlike other versions, the musical and Netflix film have their counterparts to Sidoh's Death Note owned by/bound to Ryuk. This is especially clear in the musical, where Ryuk grabs the notebook, bites his finger, and writes in his own blood to kill Light.