DCSS is a game about searching a dungeon for a magical McGuffin named The Orb of Zot. You choose a species and a background, get starter gear, and delve into the furthest depths of the unmapped, unexplored, randomly generated, extremely dangerous dungeon complex. There are about a dozen major areas in the world, including The Hive, The Shoals, The Abyss, and Hell itself, plus a large number of minor areas like the Ecumenical Temple and Erinya’s Garden, many of which may or may not even exist. Along the way you’ll find magical armor, scrolls, wands, and potions, none of which are identified. Putting on an unidentified ring could result in the discovery of a +5 Ring of Slaying (really goddamn good), it could result in “well, now you’re wearing a ring, and you still don’t know what it does”, or it could result in discovering you’ve just donned a Cursed Ring of Hunger and you’re about to starve to death if you can’t get rid of it immediately.
Death, in DCSS, is a major event. When you die, that’s it. You’re done. That character is deleted. There are no save points, there is no reloading. Want to run full speed through the Hall of Blades just to find out what happens? What happens is that you get chopped to bits by the magical weapons filling the Hall of Blades and now you have to start over.