In Baldur's Gate 3 YouTuber into the game's out-of-bounds secrets, he revealed a super-niche Act Three world state that beggars belief, one where the tiefling refugees are all zombie versions of themselves, but show up in their usual locations acting like you saved them. This requires indulging in a quite frankly deranged combo of "good" and "evil" playthrough choices:
- Save the tieflings in Act One.
- Do not save the Moonrise Tower prisoners in Act Two.
- Give the Nightsong to Balthazar
- Don't kill the hostile zombie tieflings in the Mind Flayer Colony.
This strikes me as less of a "working as intended" situation, and rather a quirk of Larian's unique way of handling NPCs. Outside very specific circumstances, each character has one consistent "actor" that's used through the entire game, rather than a new instance of the NPC for each appearance.
So killing someone in Act One doesn't set a flag to keep them from appearing in Act Three, the NPC just won't be around to appear in the first place. It's also how a merchant like Dammon will still have items you sold him in the Grove when you find him in the Lower City.
The zombie tieflings are apparently set up in the same way—the zombies are the "same" NPC as their living versions, rather than new actors. If they survive the Colony encounter, they're switched [[link]] back into a non-hostile "we were saved" mode for Act Three, just with the zombie aesthetics maintained, as the game doesn't recognize them as "dead."
This is far from a desirable world state, as you miss out on great quest rewards like the Potent Robe, but it is very funny. It reminds me of the ending of Shaun of the Dead.
SlimX's investigations have produced all kinds of strange BG3 revelations, like the fact that there's a you can [[link]] summon by murdering the comedian of the same name and jumping through some other hoops.