I wrote this up a while ago, and then forgot to post it. A few notes about how Death works in Sandman canon, and how she might fit into other interpretations of death in other canons. ☥
(Warning: teal;deer possibly lurking behind the lj cuts.)
Sandman Canon:
* Death of the Endless is the universal personification of death itself. She came into being when the universe was born, and will the last one there when the universe dies.
* She is not a god. The other
gods of death (Hades, Anubis & Osiris, Odin, etc.) still exist and still preside over their specific realms. Death of the Endless does not belong to any particular culture or religion. Likewise, the death gods do not work for her. She's an independent agent. She does not exist because people believe in her, she exists because death exists in the universe.
* She does not decide when someone dies and she does not actually cause their death. (However, judging from the times she has subtly threatened others, she probably could cause a death, if she really wanted to.)
* When someone dies, Death is there to take them to their afterlife, whatever it may be. If the person who died was Christian, for example, she would take them to Heaven or Hell. However, she does not actually decide where someone goes after death. That's up to the person and their own belief system. She's just the guide.
* She never tells anyone what's going to happen after their death. They find out when they go.
* She can decide not to take someone (see: Hob Gadling, Orpheus). That person would then live until they tell her they're ready to die. (Or tell another one of the Endless, in the case of Orpheus.) Be careful what you ask for though. Orpheus is beheaded, but continues to live on for centuries as a disembodied head.
* She can also agree to defer a death, or take one life in place of another (see: 'Death: The Time of Your Life').
* One day every hundred years, she spends the day as a human. (People still continue to die on that day, so some aspect of her continues to work.)
* Once, a long time ago, she decided not to do her job any more. No one died until she changed her mind and started doing her job again. I think this would have to be a conscious choice though. People don't stop dying if she's momentarily distracted.
* When the dead are let loose from hell in 'Season of Mists', she is extra busy getting them sorted out and keeping up with the newly dead.
* In 'Endless Nights', there is a group of people who have hidden themselves on an island to avoid death. She is shown waiting outside the gate. Once she is able to enter, she points out people and speaks of how they died. As she does, they proceed to die in that manner.
* She isn't shown hunting down other "immortals" in the Sandman canon, so presumably she only gets involved if someone has managed to "bend the rules". If they've gained immortality in some defined and accepted fashion (eating a specific fruit for example) then it's not her business.
* In the first volume of 'Books of Magic', Mister E takes Tim Hunter through time to the end of the universe. There they see Death saying goodbye to her brother Destiny as her last act before ending the universe. Destiny fades out, presumably dying. Death then has to send the two travelers back to their proper time before she can shut down the universe itself.
~*~
So how does that fit into the different views of death in other canons?
First of all, she's not going to claim that she is the boss of any and all things death related. She doesn't work that way (and from a meta standpoint, that would be both godmodding and rude).
Technically, Death of the Endless is an example of a
Psychopomp, one who escorts newly-deceased souls to the afterlife. That doesn't mean that she supersedes those from other canons, such as the shinigami of Bleach and YnM. She's not going to claim to be doing their job or claim that they're working for her.
I look at it as she is probably the one that shows up if there is no other psychopomp figure relevant to the person who has died. So if a character has a death experience specific to their canon, then she would not be involved.
Also, she is not involved in the weighing of souls or determining their afterlife. So if there is a specific afterlife experience for a given canon (reincarnation, being condemned to hell, becoming a shinigami), she has nothing to do with that.
It's entirely possible that not everybody who dies remembers her, so although she will know characters who have already died, they do not have to recognize or remember her. (But they are welcome to, if the player wants to.)
Other functions related to death, such as defeating hollows or tracking wayward ghosts, are not part of her job either. Once a soul is dead and moved on, her job is done. So if someone has become a vampire, or a ghost, or escaped from their afterlife, or is returned from death for some other reason, she's not going to be tracking them down like some kind of immortal bounty hunter. (I would imagine she could "lay a ghost to rest" by taking them to their afterlife, if necessary, but it's not part of her normal responsibilities.)
As for other, more generic pesonifications of death, like Discworld!Death, I don't see it as any kind of hiearchy, where one is senior to the other. They just exist together.
~*~
And a few Island specific thoughts.
Since the Endless can be everywhere at once, Death is still everywhere, but also on the island. It's like the Death on the island is the primary aspect of her, but there are other aspects still out in the world performing her responsibilities. (Maybe they're just on auto-pilot?)
Could the island really trap one of the Endless? Maybe, maybe not, but if not, it would be against the rules to say so. She's definitely not going to run around saying she can leave anytime she wants to. This one aspect of her is on the island and is going to stay on the island. Is that her choice or the island's doing? She'll never tell, and she's good at keeping secrets. ;D
Since she can transform herself or her reality at will, she created a home for herself. It started out fairly small, probably resembling a
normal apartment, which is what she prefers for her "realm". Now that she's sharing it with Dream, he's glitzed it up a bit (and added a throne, because he's like that), so it's probably bigger.