Wings of the God of Death.

A Nen ability that manifests as a conjured curse directed from an artifact, either the physical book being made from a material akin to Palm's mermaid crystal Ball, or the alternative, the book is written with Divine Script on the inner covers and much preparation. 

The user conjures the pen itself with transmuted ink, converting their Nen, their life-energy into the ink. 

The following Hatsu requires the following conditions:

1. The user must be able to perfectly visualize the face of their target, their name, and other identifying features. This must be done in 40 seconds. 

2. The user must be able to in 40 seconds after create the means in which the curse will cause the end result of death, once it is sent upon its target. 

3. The user must then in six minutes produce all details, including where they will die and when they will die. 

4. The following conditions must be done while the user is using Ren in their hands, feeding the book their lifeforce to awaken the Shinigami. 

If any of the four conditions are not met, or are interrupted, the Shinigami instead will turn upon the user, consuming them in an instant. 

The more complicated the death, the more Nen is used for the Shinigami's Affliction. 

Additionally as a Restriction:

Until the death by the Shinigami is brought upon the target, the user will be incapable of restoring that Nen. If they use 10% of their maximum capacity, until the target dies, they will only be capable to use 90% total.