AD&D: Apocalypse When?

♫It's the end of the world as we know it♫

AD&D is a post-apocalyptic game by default (as has been noted before) and much of the fiction listed in Appendix N and fantasy fiction elsewhere has some post-apocalyptic aspect. REH's Conan stories are set in a Europe which is recovering from the sinking of Atlantis, a setting repeated to drastically different effect by Tolkien's Lord of the Rings. But many of the other entries in Appendix N are set sometime after a "golden age" of some kind has come crashing down in flames or, as in flavour-of-the-year Game of Thrones, ice.

For the game as originally envisioned, this is an ideal set-up as it gives in-built reasons for various things that Gygax and Arneson wanted in play. Firstly, it implies that current technology is limited, so mediaeval weapons and armour are the norm despite the recorded history of the world being quite deep and the Golden Age presented as being very advanced in one way or another.

Secondly, it means that the "civilized" parts of the world have at some point shrunk drastically. They may be recovering but there is a feeling of a candle in the dark. This can give characters a motivation both to go out and explore and also to push back the boundaries of the "wilderness" and re-establish civilization, both goals that were explicitly stated in D&D from the very start. It also means that there's lots to explore.

Bow before the Green Witch

And where the characters go out into the wilderness they will find the ruins of the pre-apocalyptic world - things that they call castles, dungeons, and ancient cities but which could, to their builders, have been research centres, bomb shelters, and fields of generation ships which were never launched to the stars (this one is from Tekumel, surely the greatest apocalypse of them all with hundreds of entire solar systems sucked out of our universe and into somewhere else, each completely isolated in a sky with no stars other than their own).

Inhabiting these ruins are of course the monsters - the things which are no longer "normal". Were they normal Before? Were gnolls simply pets to the Ancients? Perhaps the monsters are a result of the apocalypse; perhaps they caused it. Similar questions may be asked of the gods; in my CSIO campaign the god Mycr was based on the computer "Universal AC" in Asimov's short story "The Last Question" and was the reason that the Apocalypse (the group, not the event) had failed to destroy the world and instead created Gamma World.

High Level Ranger

And what are these monsters guarding if its not the Lost Knowledge of the Ancients? Well, apart from the Lost Gold of the Ancients, of course. The Ancients could do things that can not be duplicated now - they made the artefacts and even some of the non-unique magic items are still beyond the ability of the greatest magic users of the "modern" age. This is embodied in the difficulty of making magic items in the DMG - if making one's own items was too easy, then a chunk of the motivation to go out and try to dig up ones already made would be gone.

The dead past thus represents the origin of threats (monsters) while holding out a possibly false promise of a quick-fix for that threat in the form of read-made magic items.

This dead age can also be used more directly to produce adventure hooks - certain beings may have survived, perhaps in suspended animation or perhaps simply immortal. Or magic can open a rift, allowing characters to travel back to the lost Golden Age where they might find that all that glistens is not, in fact, gold - potentially a complete reversal of the Dungeons and Dragons cartoon show where D&D characters try to escape from a much more advanced world than the one they're used to, and return to a world of simple magic and flying horses.

Old School End of the World Checklist (other old-school checklists are available; time invested may not pay off; offers not valid in some dimensions)

"We're not kobolds, okay,
Mr Monkeyboy?"

• When did the old world end? Is it within human memory? What about elven memory? Will almost any exploration turn up evidence or is it only the deepest levels of the deepest dungeons that carry a risk of encountering Horrors from the Past™?
• What sort of world was it? What sort of ancient artefacts might show up? It's true that the things listed on the magical tables are, duh, magical but maybe there's other options even there. Keoghtom's ointment may in fact be a product of nano-technology; bracers of defence some sort of force-field. But beyond such terminology changes, the DM can sprinkle one-off items around which evoke both the promise and the dangers of the past, whether canisters of viruses or demons enslaved to power flying machines.
• What destroyed it? Perhaps it's something cyclical, like the thread of Anne McCaffrey's Pern stories - if it is, when can it be expected to happen again? Perhaps it was some other natural event like the sinking of Atlantis. Maybe it is something that poses some indefinite future threat like Ksarul/Tharizdun or Cthulhu, waiting for something to free them from slumber to finish the job. Maybe it was the arrival of magic itself, or the gods. Perhaps a war of some sort between wizards and clerics or between dragons and humans, elves and dwarves (leaving the stage clear for humanity), or Law and Chaos.
• Do people know what happened? If not, does anyone care and should they? Is there a stigma or taboo connected with things recovered from "the wastes" or are such items required by law to be handed in to the authorities under pain of, well, pain? Are there sages which know, or are willing to pay for expeditions to find out?
• Is the Apocalypse actually over? The game assumes that the players will, even incidentally, cause the wilderness to retreat. But perhaps it pushes back; perhaps there are intelligent forces out there still trying to harness whatever created that wilderness - organized and intelligently led parties who are themselves exploring dungeons for weapons in a war that civilized people don't even know is being fought.
• Are there survivors, and if so where and what are they? Are they individuals or perhaps an entire race, Silurian-like, expecting to return to a position of rulership once their agents feel that it's safe to come back to the surface?
• Why did anything survive? What did the people at the time try to do about it, and what weapons, artefacts, spells, monuments etc. might remain of this effort? Was the final end only delayed? To what extent are the monsters of the wild simply the descendants of things which were commonplace Before?
• The ultimate question: could someone that knew enough about what happened deliberately cause it to happen again?

"When my horoscope said 'The stars are right',
I assumed that was a good thing!"
"Shut up and row."

Some of these questions can be answered in ways that tend to lead to over-arching themes but mostly they have answers which will only influence the tone of what is found underground and in the wilderness and I've not tried to give examples of the really off-the-wall possibilities such as might be found by a close look at Alice in Wonderland or Bagpuss. Writers, and myth-makers, have found the idea that we are living in the tumbled-down remains of some Cyclopean past (literally, in the case of Greek mythology) a rich inspiration and from Plato to Tolkien to, of course, Jack Vance it has provided a backdrop to some of the world's best fantasy stories and D&D is largely designed to allow interaction with exactly that sort of backdrop. Simply running down the list above should spark ideas for races, magic items, spells, patrons, dungeons and towers, and special encounters.