I wanted a break after focusing on my randomly-generated dungeon series, so I thought a return to this miniseries would be a nice palette-cleanser. As usual, the idea here is to make a roll with TVTropes' "random trope" button and see what ideas in inspires for things I could do in a TTRPG (generally D&D-like, though I'm not holding myself to that explicitly). The standard goal: six italicized ideas that could be put into play, together with my initial thoughts on the actual implementation.
Today's random trope result: Unwinnable by Insanity
Well, that's a bit of a stumper, at first glance, but I think I'm up for the challenge. The heart of that trope is a person putting themself in a situation where they're unable to achieve their goal, either categorically or at least without some seemingly-divine intervention, by doing something stupid (in hindsight, if not at that moment). After some mulling on the topic, the first thing that comes to my mind is the captive creature that the PCs can release with adventure-derailing results, such as the trapped wizard in Tower of the Stargazer. That's not quite as severe as the actual trope, but as I said with Matter of Life and Death, the trope is there to inspire ideas, not to bound them. Alright then, let me see what I can do with this:
1. The Chosen One is Dead
"The lone solace of the people in bondage to the iron rule of the merciless tyrant lich was a prophecy foretelling their imminent deliverance at the hands of a fated child. Unfortunately, one of the child's siblings enacted a foul sorcery in a fit of jealousy, reducing the prophesized savior to dust that scattered on the wind."
I'm usually not a fan of "chosen hero" plots for TTRPGs, since they tend to be quite fragile on top of encouraging railroading. In this case, though, I think it can work. Set up a sandbox under the rule of some distant overlord, add some reason about why only the third son or fifth daughter or whatever of their mortal nemesis can strike them down, kill that person, and then turn the PCs loose. For added fun, leverage that pit fiends and glabrezu/type 3 demons are capable of casting Wish in AD&D.
2. Pandora's Box
"In some remote part of a dungeon is a room where a pagan idol watches over two sarcophagi. One is plain and contains offerings of material wealth from the idol's worshipers, along with magic of animation and divination. The other is inscribed with copious writings in an ancient language and contains a heretic of the cult, transformed by divine magic into an immortal agent to spread the idol's corruption. The heretic is imprisoned helplessly unless the sarcophagus is opened."
This is basically the set-up I used in my Twisted Lovers adventure (for which I really should update the write-up at some point, but I digress), though in order to enact the target trope, it should be placed in a dungeon where it's mostly incidental to whatever else is down there, perhaps being a lost and buried temple that was breached recently. The monster need not actually be immortal, of course, but it should be both powerful enough to overwhelm the PCs in direct combat (at least initially; let them have a chance to overcome it if it becomes a campaign focus by their choice) and slow enough that fleeing is possible. Don't bother with this if you've trained your players to approach all monsters as hostiles to be fought to the death.
3. Sealing the Door to Before
"The dungeon has a choke point (either at its entrance or between sections) flanked by a pair of steel statues. Further on in the dungeon, there are two things: a trigger unrelated to the PCs' goals that will animate the statues into sealing the choke point, and a monster that can destroy steel."
Inspired by inverting set-up of the door-wielding statues from the tomb below the Shrine of Amana in Dark Souls 2, the execution here mostly speaks for itself, I feel. As with the trap room idea from Matter of Life and Death, the severity of the trap depends on how many alternatives there are to the obvious solution of luring the monster into destroying the seal. Don't bother with this if you're not tracking resources and/or if you've trained your players to approach all monsters as hostiles to be fought to the death.
4. Curse of Pride
"The robber thought they were clever, very clever indeed. In order to set up a theft at a temple, they hired a group of scrupleless mercenaries to kidnap the priest, talking them into accepting a lower payment up-front as the robber swore to pay the ransom immediately afterwards. However, the robber did not anticipate the demon bound within the reliquary. In order to escape with their life, they had to strike a foul bargain, one which left them unable to part with their ill-gotten gains. Now, the priest is dead, the mercenaries want the rest of their dues, and the robber is left unable to be rid of a treasure that would land their head on a pike if discovered."
Ah, now that smacks of something straight out of some pulpy swords-and-sorcery story. A few options for how to go with this one: (a) the usual method of having it happen as a background item leading to rumors that the PCs can follow up on, (b) the PCs could be approached by either or both of the main parties for their aid, (c) the PCs are given the stolen relic by the robber and so become the target of both the mercenaries and the demon's bargain, or (d) the PCs are the mercenaries, and this whole idea is the reason behind why someone tried to skip out on paying them their balance (killing the priest is completely optional for this approach, obviously). The big question to be filled in, of course, is what the terms of the demon's bargain were. Be devious.
5. The Exchange
"Ages ago, the proprietor was merely second in line for their current seat of power. In order to eliminate their competition, they enlisted the help of a faerie, who requested only a lock of the proprietor's hair in return for making their competition disappear. The deal had seemed to work out wonderfully, drifting off into lost memory, until a stranger arrived recently, looking like a twin of their competition but with hair matching the proprietor's. The stranger's business cut a swathe through the proprietor's profits, but their knowing smirk has been the real cause of the proprietor's insomnia."
This one writes itself, I feel. Add in rumors of their relationship and advertised interest in eccentric "professionals" to suit, and adjust the scale to taste (e.g. instead of a business squabble, perhaps a ruler who's allies are being swayed by a charismatic demagogue). Is the newcomer actually connected with the competition/the faerie, or is their appearance merely a coincidence? What did the faerie actually do?
6. Death Ouroboros
"None dare tread upon the site of Ascar's fall, for each night, spectral armies rise to recreate the infamous battle. A single skeleton fights amidst the spirits, the lone source of sounds at the scene, their cries of agony as they're cut down falling silent just before dawn. Legend says the skeleton is what's left of Ascar, and the only way to end their suffering is to find a way to change the result of the battle."
The trope's page makes many mentions of video games that allowed the player to save just before a then-avoidable death, so it made me think of the classic curse of someone doomed to relive their death over and over. That, in turn, made me think of one of the hex entries in Joseph Manola's Sacred 2-inspired hexcrawl having two spectral armies fight each other over and over. Take that idea, add a central figure, and it's a mix of the two. What's the story behind the battle? What caused the haunting to happen? Is either part of the rumor actually correct? What could lift the haunting?
Honorable mention: Seeing as I did make a couple of posts about modifying that module, I would be remiss if I didn't mention that I3: Pharaoh can work as an example of this trope, if you play up Amun-Re's curse instead of (or in addition to) encouraging an insurrection against the ruler in charge of the desert bandits.