Minecrafter!Reader in a SAGAU World (Shenanigans)
Imagine how wild Minecraft potions would be in Genshin.
Vanilla Minecraft potions are already crazy on their own but imagine modded Minecraft potions? Specifically the Potion Core mod, Not Enough Potions mod, Witchery mod, Botanica mod and the Extra Alchemy mod.
In the Cult AU, any character who works in alchemy or at least has some interest in the art of potion making would be fighting tooth and nail for a chance to study under you.
There'd even be a few who are interested in testing out those potions for you since you'd need to adjust and change some parts of the formula to be more accustomed to Teyvat (after all, you likely wouldn't have access to most potion ingredients there)
And on the other hand, the Imposter AU
It really depends on your morality here because I can see a few people choosing instant violence and just causing mass genocide. And potions are just one of the few methods you can use to wipe out the populace.
Then we have the part where you can just be silly. Y'all know Dream's manhunt? Yeah, that's the energy here.
Shenanigans are aplenty as you do everything in your power to avoid capture.
Mileleth: Surrender yourself, imposter!
Reader, cornered in a cave: Oh no.. it seems like this shall be my demise.. OHMYGODISTHATTHECREATOR!??? (Points to the cave exit)
Mileleth: (looks at where the reader is pointing)
Reader, pulls out an invisiblity potion: SEE YA, SUCKERS!! (Immediately downs it and disappears)
The Mileleth are panicking over your disappearance while you sneak away.
Almost anything could go here, really.