Perhaps as a consequence of my getting older, over the last few years I've become increasingly fascinated by memento mori artwork. Granted, this fascination is deeply rooted in my psyche, going all the way back to childhood, but it's intensified in recent times. The phrase memento mori itself is very old, predating Christianity, which adopted it with great vigor, particularly during the High Middle Ages. Something like this phrase was reputedly whispered by a slave into the ear of a Roman general receiving a triumph and, of course, every Ash Wednesday, I'm reminded that I am dust and unto dust I shall return. There's also the tradition of the danse macabre, which carries off prince and pauper alike.
I bring this up primarily because I've noticed that my Dwimmermount campaign has included lots of little references to mortality and attempts to escape it. The cult of Turms Termax, sees death as an obstacle to be overcome, following the example of its founder. So far as anyone knows, no Termaxian adept has succeeded in achieving what Turms reputedly did, unless one counts the numerous undead beings devoted to the cult. In the campaign, many of D&D's familiar undead creatures are the result of mortal beings attempting to achieve immortality through some despicable means, often at the urging of demons, who tempt Men by reminding them, like those slaves in Roman times, that they are mortal. Ghouls, for example, are human beings who have achieved immortality -- and eternal hunger -- by indulging in cannibalism. It's not a pretty sight.
The player characters have bumped against the issue of mortality in other places too. With the exception of Vladimir the dwarf, no dead character has ever returned to life and he remembers nothing of "the other side." Speak with dead was once used, but I've ruled that the spell doesn't enable conversation with the dead person's soul at all. Rather, it simply grants limited access to the memory of the deceased, which lingers within its corpse. That's why the spell only works if there's a body and only a fairly recently dead one at that (as per Supplement I rather than later versions). The question of mortality and the afterlife came up too during the characters' meeting with Xaranes, who mocked the notion that "the Great Maker's handiwork should be as perishable as your kind seemingly suppose."
Dwimmermount's just a D&D campaign; I don't intend it to be a "deep" meditation upon the human condition. Still, these little elements have added some nice texture to our sessions, making them both enjoyable and memorable. They also add mystery, as the characters now have lots of contradictory evidence to support all kinds of perspectives on the matter of mortality -- just like real life.