What would happen if you wrote 'dies of natural causes at any time after the next week'? After all, the Death Note-inflicted death isn't natural, and since you haven't specified a time, would it default to your original natural death? Accidental death doesn't seem like a natural cause either, so presumably it would have to be old age or something like that.

So what if Light writes into the Note that Raye Penbar will carry out every instruction given to him by 'stranger who claims to be Kira and speaks to him through the earbud,' and then, when Raye gets into position and wears the earbud, give him impossible-to-fulfill instructions such as get to Eiffel Tower in 1 hour? Would Penbar drop dead (heart attack) after hearing the impossible instruction, or would he drop dead 40 seconds after Light finish Raye's segment and thus never showing up at the train station? If it's the latter, is the Death Note universe predeterministic?

The Death Note defaults any improbable cause of death (or actions taken before death) to a nondescript heart attack, without the victim carrying out ANY action at all, the mundane ones included, even when ONE improbable component is present.

The lack of stimulating activity is Ryuk's primary reason for dropping Sidoh's Death Note into the Human World. This is a result of the realm having very little food and them evolving over time to not require such sustenance. They also pass time by eating, though they have no need to. They are typically seen gambling with one another, watching the events occurring in the Human World through the spheres or terminating human lives with their Death Notes in order to prolong their own.

Ryuk explains that there is not much to do in the Shinigami Realm. These artifacts have openings that let Shinigami see anywhere in the Human World from a birds-eye view and are what allow Shinigami to take human lives with their Death Notes without traveling to Earth. The spheres, which are shaped like concentric orbs, are littered about the surface. The realm is surrounded by deserts that have various strange objects.

There is at least one mountain with aР’В cave structure where Ryuk resides in the Relight OVAs. There are also many chains, surrounding both commonР’В areas and the Shinigami King's cave, where there are hundreds of chains with hooks on the end. Shinigami tend to congregate in areas with bone and stone structures. The realm includes different landscapes and lacks modern infrastructure. Sentient beings other than the Shinigami do not appearР’В to exist there. Plants areР’В never shown, though they do exist, as Ryuk brings an apple from the Shinigami Realm to the Human World, although it was shriveled and unlike apples found on Earth.

Very little vegetation is found in this barren land. Ryuk holding an apple from the Shinigami Realm. This is further shown when Ryuk is first seen in the Human World after leaving the Shinigami Realm, flying down from a higher altitude than skyscrapers. Ryuk has to travel underground in order to reach the entrance to the realm of humans underneath. The world that Shinigami reside in exists in a plane above the Human World, inaccessible and unseen through conventional methods.

Shinigami eating apple laptop sticker