I'm running The Wild Beyond the Witchlight and I'm slowly adding in lore about Tasha for my players to learn. I can't seem to find much of anything on this topic other than the fact that they're frenemies and sometimes play chess.

A relatively well-known D&D example is the Blood War between demons of chaos and devils of law. There are many other possibilities. Maybe an important bulwark that defends the land from a demonic invasion is the undead army of some lich king, who would prefer to dominate the world rather than see it fall into fiendish hands. Perhaps the primordial titans have shattered their bindings and are devastating the planet with flames, storms, quakes, and waves, but eldritch hierophants and cultists call down alien horrors from beyond the stars to defend civilization: for elemental annihilation is not, in fact, the "correct" eschaton. On a much smaller scale, perhaps the shady criminals in town can be convinced to steel themselves and help hunt down the man-eating werewolf terrorizing said town.

What are some memorable examples that you have seen or created, and how did the PCs get involved?

I have been considering a setting where one of the main quirks and threats, maybe the biggest, is that rulers who attain a certain threshold of glory, renown, adoration, etc. apotheosize into minor gods. With their vastly superhuman abilities, they can lead their people to greater heights.

But a minor god can still die, whether in battle, to assassination, to mystical cataclysms, or to the most pernicious of poisons and curses. The ruler becomes a malice- and resentment-driven undead overlord. Some cling to their people maniacally and overprotectively, while others turn on their subjects due to some perceived slight, such as failure to prevent the ruler's death. This is always a dark time: wars ignite, plagues and famine strike, lesser undead rise, and reality-rifts disgorge horrors.

They vary in form: skeletons, zombies, vampires, ghosts, some in between. Twice, an apotheosized ruler entombed themselves deep beneath the earth, all "king asleep in mountain" style. One was assassinated regardless, rising up as a wraith. The other still lives, fearful of death, yet willing to aid their nation in a dire time.

Legends hold that a few of these overlords, for whatever reason, elected to simply leave the mortal world. They gathered in the Negative Energy Plane. This small circle of long-undead rulers has been concocting some scheme through which they may optimally reclaim the world that they departed from. Do they also plan on backstabbing one another? Probably.

What would you do with such a setting? Would you have the PCs start in a nation whose ruler just became one such undead? Would you have them start in a nation externally imperiled by an undead overlord: perhaps while their own nation's ruler is a still-living minor god, worried about dying? Whatever the case, I imagine that PCs could be the ones to finally unearth the source of this phenomenon and break the curse once and for all. (Of course, even a still-living great ruler can be a conquest-minded villain...)

I find the recent Genshin quest about a memory-artificer and her daughter to be very memorable, and I would like to import it into my ongoing game.

Let us start with a warning, first off: the quest involves child abuse and gaslighting. Any players will have to be vetted to see if they are fine with this.

To significantly simplify the quest into its most basic form (and taking a few liberties with the order of events), the party meets a talented artificer. Her specialty is crafting items that record memories, and the party has some sort of pragmatic or personal interest in this.

The artificer happens to have a daughter. The artificer explains that the daughter is sickly, suffers from memory loss and delusions, and sometimes says strange things (#1, #2, #3).

The party gets suspicious and investigates. The inquiry is complicated by the people in the surrounding community having only spotty, hazy memories of the artificer's daughter. The party is resourceful, though, and manages to reconstruct a disturbing sequence of events.

The artificer's biological daughter died years ago. Shortly afterwards, the grieving mother adopted an orphan with a similar appearance, and renamed that orphan to match her original daughter's name. The artificer mundanely groomed the orphan to pretend to be her original daughter. Eventually, this escalated into the artificer drugging the orphan towards greater pliability. This further escalated into the artificer lining the orphan's bedroom with crystals containing copies of her original daughter's memories and personality, designed to gradually overwrite the orphan's own memories and personality. Between the drugs and the crystals, the orphan's physical and mental health declined, thus doubling as Munchausen syndrome by proxy. All this unfolded over years.

The people in the surrounding community have cloudy memories of the artificer's daughter (and therefore have a hard time realizing discrepancies) because the artificer was distributing her crafts amongst them. They were secretly designed to absorb memories of the original daughter.

The party confronts the artificer and her "daughter," but the artificer is ready. Using some sort of doohicky, the artificer and her "daughter" are whisked away to some secret lair. The party fights their way through the workshop, where they see the artificer ready to undertake the most extreme step possible. With the help of a large cache of memory crystals, the artificer's ritual will fully rewrite the orphan's memory and personality with those of her original daughter. The party has come all this way; they might as well stop the ritual, save the kid, and apprehend or kill the grieving mother.

I find this compelling. I think it would make for an interesting scenario in a tabletop RPG. Do you think it could work well? How would you try to get the party invested in this scenario?

Some extra thoughts: This quest has an inherent degree of resistance against unexpected action, mostly because the artificer and her "daughter" can contingently poof away.

For example, if the party were to aggressively accuse the artificer on their first meeting, she and her "daughter" could feasibly poof away. Then the party would have to track down the lair regardless, reconstructing what had happened regardless.

There is also a degree of resistance against lie detection abilities. Namely, the grieving mother's mental state is such that she sincerely believes her own fabrications to an extent.