More years ago than I care to remember I wrote an AD&D module for a tournament. It was a fairly standard conceit, in that it opened with the Bad Guys™ raiding the palace of a city and kidnapping the princess from her tower. The players, being the first responders on the scene, arrive on the tail end of this event, just in time to witness the bad guys make their getaway. After dealing with the rearguard, they have the option to pursue immediately themselves (something the gamemaster should encourage), or organise a proper rescue party. [If they did the later they'd automatically "lose" the tournament btw, as they could never catch up to the kidnappers, but they could still have fun as the module bifurcated heavily at that point. (They were warned).]
The fun bit was the freedom of choice offered to the players, because we allowed them to build their own characters (using the rules we provided) and take whatever equipment they wanted. Often the players got to run the same characters in two completely different dungeons (I'm not sure if this was the case with this one as I wasn't present at the Con where it ran). This could end up with, say, a party deciding that 4 druids (plus 2 other classes) was the way to go and ending up in a situation where most of the druids special abilities don't really come into play.
What I also enjoyed about this module is that it was set on the dying Mars (and where, in pulp SF conceit, Earth is inhabited by Stone Age primitives and Venus by dinosaurs). Fighters and thieves could translate almost untouched. The spellcasters used the remnants of the lost technology to duplicate the powers of spells. Magic users became "Scientists" who had a rote understanding of how such arcane devices worked and could create their own if they found the right parts. Clerics became the "Engineers" who through their devotions and under the command of their God(s) ran the cities aging support infrastructure (there were many cities which had been abandoned because the gods had withdrawn their favour), and could commune with the City God (or gods) in their Temples. And because you can get away with a lot more in a tournament than you can in a campaign, spells were single-use devices. So instead of having memorized the spells, it represented the devices that the spell-casting character was carrying at the time of the raid (and whose secret of operation was jealously guarded secrets). It lead to the interesting idea that players could regain unused "spells" from the body of their spell-casting opponents (after they had disarmed the requisite booby-traps that were a standard amongst Scientists who jealously protected their secrets). And yes, spellbooks were coded design schematics for devices. It also explained why the cleric with the party was most probably from the Order of Medik from within the city cult/temple.
Similarly the basis of the various demi-human races changed (they were all engineered off-shoots of the
Anyway, I wrote the module on this basis, beginning with a skimmer chase across the desert in pursuit of the kidnappers, with encounters along the way, and a final confrontation with the kidnappers. [Or if they waited and formed a proper posse, they got to have fun stomping around the desert with troops, lots of spell support, and eventually realise that the kidnappers had made their getaway. Fortunately everybody apparently took the rather pointed hints that they should immediately grab the remaining raider's skimmer (after having killed the rearguard), and pursue. But I don't like forcing people, so I gave them the choice.]
But I wrote a lot more background than was really needed for a tournament module. Especially one built on the pun that "magic" swords and armour were manufactured from various grades of a material called plas (plas wun, plas doo, plas ree, plas orr, plas phi), and the idea that anyone could use a standard magic wand (a pistol) or a magic staff (a rifle) [although there was always a risk with such valuable relics that something might go wrong, and recharging or fixing one was a dedicated job for a Scientist, often needing resources that were zealously guarded by the temples (Scientists had inherited the blame for the world dying and were generally looked on in suspicion by most, especially the Engineers)]. Because I found the word quite attractive as somewhere to adventure. There is always something intriguing about breakfasting in the ruins.
It's surprising how many people take an unreasoning dislike to roleplaying in a science fantasy D&D game (in general, I was never told if people freaked in the tournament, and the feedback I did get was that people thought it was fun). But it's a fairly standard trope from the very beginning of the hobby. Dave Arneson's Blackmoor campaign featured more than it's share of ancient technological artefacts (such as The Blue Rider's impressive strength-enhancing magical armour and flaming sword), and even Empire of the Petal Throne's Tekumel was originally a struggling colony that had been cut off by some cosmic catastrophe from it's space-faring roots. Not to mention it was also a standard trope of the fantasy of the time. [Many people credit Tolkein as being the inspiration for D&D, but whilst it had a profound impact on the wargames that D&D grew out of, I always found that D&D owed a lot to the pulp fiction of the time as well.]
Why do I mention this. Well I've come to the decision that I'm not going to reboot my old D&D campaign, because it's tied too closely to the players who created it, and most of them are no longer around. So that leaves me looking for alternatives. I do like the idea of The Crater, which is the source of all magic in the world as a traditional megadungeon, but since that was envisaged to rely heavily on the third dimension (pathways clinging precariously to the sides of the crater with minidungeons and even entire towns carved into the sides of the crater). And good 3D design is something that the tabletop doesn't really do well, and probably best done with miniatures, especially with floors mounted on polystyrene blocks for height. And I don't really do miniatures. And there is an intentional separation from the wider world in play there, since the "Empire" is struggling to maintain control of the outpost there, especially in light of the hostility of the surrounding nomad tribes who believe The Crater is taboo and keep raiding the supply caravans (and any magic prospectors that they can find). And yes, it is more than reminiscent of Pavis (Runequest/Glorantha) for the set-up; that's because Pavis is such a brilliant adventuring idea. And I'm thinking I want something with a bit more campaign interplay in the style of my old campaign.
And I've just been reading the excellent dungeon module Anomalous Subsurface Environment by Patrick Wetmore which makes me want to revisit a similar theme. The Orbital Gods are such an excellent idea, and they remind me of the City Gods of the Martian tournament. And City States are so much easier to do in D&D.
The main problem is that, whilst my trick for dealing with spells worked well for a tournament module (since there was no effective difference between a mage memorizing a spell that disappears on use and a one-use magical device that must be activated, the application of such a distinction in a campaign is less clear, and may result in a fundamental change in the nature of the game. If it becomes a simple game of searching the ruins of the past for Lost Tech then it simply becomes another Gamma World, which is what I don't want.
Although truth to tell, probably nothing will come of this either, besides copious notes, but then, it's a good thing I do like constructing worlds. The interplay of the necessary systems required to get the world to live on it's own has always fascinated me.