Do you have a particular definition for 'fantasy world' in mind here?

any fictional world will do, I think? but this is specifically about AUs of preexisting fiction, not fully original worlds

Also not sure if you mean picking out an AU version of a setting that already exists, like a specific fanfic, or picking out a setting to go to an AU version of?

I mean (for all settings) picking out an existing AU that is depicted in some form of media.

So, for example, specifying "Mauling Snarks" as a Worm AU because things are a lot less grimdark and more survivable, etc.

hmmmmmmmm

I guess technically pirates has published a bit of their RWBY AU? It's a bit of a brighter and more intelligent version of the setting with a bigger magic system and cool girlfriends in it and good transition tech w/ the aura awakening process? Though it's still a good bit deathworldy, so...

We will totally take 'technically's for this purpose! And yes, I think I'd probably prefer the Pirates' RWBY AU to the canon timeline. I'm not sure how much one can actually tone down the danger of RWBY without making it not RWBY, since the protagonists are professional monster fighters.

This is true! Also not sure how much timeline control you get for this - there's a decent number of fics like that exponentially multiplying succubus AU of worm that are only particularly nice if you get in at the very end...

I'm sorry, exponentially multiplying succubus AU? I am intrigued and concerned.

A) I don't think I've read that one; do you have any other identifying details?
B) We (hypothetically) don't get timeline control; you're just ending up in a particular AU setting at some point during its timeline.

if i produce media now, depicting an AU that i just made up of a fictional setting that i also just made up, does that make it a valid target, or is that a bit too "technically"?

Provided you actually do produce the media before (again, hypothetically) a month or two from now? That totally counts.

https://forum.questionablequesting.com/threads/succubus-worm-complete.7134/ It was this one!

Thank you!

any AUs with easily accessible mary sue notebooks okay I'll stop cheating and try to find a real answer

That's definitely the best (assuming the notebook lands on somebody mostly aligned), but there are lots of settings that it hasn't gotten to yet. I guess that's actually a practical reason to go write a ton of notebook threads ...

Eh... I would seriously consider Hiver's Culture Trek

Ooh! That would be a good one. They at least manage to give the Borg a black eye in a reasonable way.

it's far from perfect but it's trying in a way I appreciate

I'm also not sure if anyone has written it but a nobody dies AU of Outer Wilds would also be super compelling

star trek is a nice place but it's also a setting with a bunch of giant wars and capricious cosmic beings in it? Not nesscarily the most stable place, and it'd be easy for some background lore element to have horrifying implications that just wasn't brough up... But it's still a relatively reasonable choice, I think? Just much to be aware of

well yeah...

Sure, but if you had to go to any Star Trek, it's a matter of which Star Trek you'd want to go to.

This particular AU is pretty low on onscreen deity
maybe stuff like that is lurking off screen

Well, at the least you'd have to deal with Q.
Actually, I wonder if "Meet Qte" would be better, since it's got a Bell trying to get Q to be helpful in it.

hmm... Q is vaguely implied with the Borg being present but isn't actually explicitly mentioned iirc
or not outside of being a thing in the simulation show
but that's not all known to be canon

Oh, maybe you're right. It's been a long time since I read Hiver's stuff, and I might be mixing it up.