“I've met lots of magic ponies. Even singing ones. I've met everybody.” - Death, DC Action Comics #894

Death comes to all things. Stars, gods, people, and even ponies. She rarely visits Equestria, but it's one of her favorite places. Something about the harmony there. And ponies almost always die when they're very old, which is a nice bonus. But she knows that makes it harder on the ponies left behind, most of them aren't used to death. So sometimes, while she's there, she takes the time to enjoy her visit, and to try to help everypony there to deal with something that seems so strange to them, but so normal to her.

Three part crossover with Neil Gaiman's Sandman universe. But the only thing you really need to know is that Death is the personification of death across all universes, and usually appears to humans as a rather cheerful teenaged goth girl.