A Reaper is a psychopomp demon created by Death in order to help him sort deceased souls into their correct afterlife. Most Reapers are tasked with being only a guide to the dead, not a judge. Reapers lack the ability to directly interact with souls, and thus are unable to compel them to follow if the soul refuses. Souls who refuse to come with the standard Reaper into their afterlife linger on Earth as ghosts. Ghosts are then delegated to a special class of Reapers, called Hellhounds, who act as the bounty hunters and forcibly drag the souls into their afterlife.
The vast majority of Reapers are employed at funeral homes or are otherwise in the funeral industry in order to have frequent access to the newly deceased, whom are often accompanied by their lingering soul. A smaller minority of Reapers are employed at hospitals for a similar reason.
Reapers are isolated spirits that Death must bind to a corporeal body in order to be on Earth. However, since Death can make spirits and not bodies, he binds the spirits of Reapers to "empty" bodies, namely miscarried or stillborn fetuses and infants. They go through an accelerated maturity before Death freezes them at adulthood. Occasionally, he can mistakenly bind a spirit to the wrong sex, resulting in some Reapers being transgender on Earth, despite having previous bodies of the correct sex.
While they are immune to most diseases and natural causes of human death, they can still kill their physical body through egregious levels of physical damage. Most wounds can heal on their own otherwise, and Reapers are able to undergo surgeries, piercings, and tattooing without any issues.
Despite it not being necessary for their survival, they possess the ability to eat, drink, sleep, and do most other human bodily activities. Most engage in these activities regularly due to the residue urge to from their bodies. The only exception is procreation, as Death renders them biologically sterile upon binding. To date, the only Reaper whom has created offspring is the Hellhound Reaper Garmr, and he had to first supply Death with a spiritually empty body as a vessel, and request a part of his spiritual energy be severed and bound to the body. This resulted in the only half-demon Reaper, Gnípa.
The only way to kill a Reaper is by Death himself terminating them. Rogue Reapers who refuse to Reap are eventually terminated. Seldomly, a Reaper may request to be terminated, and if they are certain of their decision Death will oblige.