On Terry Pratchett’s Discworld, the gods come into existence when people believe in them. Similarly, Death manifests itself as the Grim Reaper because people believe Death is a skeleton, in a hooded black cloak, with a scythe.
In Reaper Man, the Powers That Be have relieved Death of his duty on the grounds that Death has become too sympathetic of his clients (us: the dying and the dead).
They send Death off with his hourglass* and let him keep his horse, Binky. For the first time in his existence, Death has a life, and for the first time in his life, Death has Time.
And he’s going to spend it.
But first he has to get a job.
*Do you get the joke? He’s been a faithful employee so they send him off with his hourglass. It’s hilarious.
Soon after, a tall dark stranger appears on a farm in the country. It’s harvest time, he’s looking for work...and he’s good with a scythe.
Meanwhile, chaos runs through the City of Ankh-Morpork. Death (an important public service) is gone, so the dead are queuing up in the increasingly crowded space between this world and the next.
Windle Poons, a 130 year-old wizard from Unseen University, has been waiting to die and reincarnate for a long time. (So has the faculty member waiting to take Windle’s room.) But without Death to escort him to the afterlife, Windle Poons just...comes back.
As a corpse.