In this case, the door opens into a library and admits what appear to be...

a pair of small unicorns with images of a shrub and a book on their flanks.

Inside, they can see a restaurant with a bar. There are stools at the bar, alcohol lining the shelves, copious seating- seating as far as the eye can see- and people. None of them look like ponies, or dragons, or anything Gloss or Gossamer would recognize. Some have scales, others feathers, but most are bipedal. They chatter, laughing and arguing at loud volumes.

There is a spiral staircase which seems to lead up and down, and there's music playing. There is no one attending the bar.

This is very surprising.

Gossamer will go ask people what's going on.

"This is Milliways, the only bar at the end of the universe! The rest of them have gone out of business, see. People come here from all sorts of places and time periods and what-have-yous. You're like the wildest mammal that I've never seen. How'd you manage on four legs, anyway?"

"It is curious, isn't it? Can a species really manage to evolve without reaching a bipedal state? I can scarcely credit-"

"Evolution can't be real in every universe, Erdiga. Perhaps this...horse...comes from a universe without it. If I were to venture a guess-"

The three of them continue arguing, forgetting the source of the argument. Their remaining dining companion exhales a noxious cloud, which seems to communicate quite clearly to Gossamer despite the lack of any vocalization:  "You should talk to the Bartender. They'll keep on like this for hours."

Well, she doesn't see a bartender but she can go wait for one at the bar. And also relay what she heard to her sister.

The bar might sense that, while she is capable of eating material food and drink, doing so gives her neither sustenance nor pleasure; she instead lives by magical parasitism.

If the bar senses any such thing, it does not say as much. The suddenly appearing Bartender, a portly gentleman with several tentacles extending from his back, says, "Welcome to Milliways! What can I get for you, madam?"

"I'm told I should ask you what's going on?"

"Ah, yes. A first time visitor, are you? Well done, well done. This is Milliways! We cater to patrons throughout every universe. No matter what point in time or point in space you come from, we welcome you. Oddly, some points of time and space seem the same yet contain different sorts of things. Most patrons talk about different universes or dimensions or worlds, although I'm afraid there's no truly consistent terminology that I'm aware of! So you could be from the same exact time, down to the minute, and in the same exact place on the planet, as another patron, but you might have completely different physics or magics! The drinks and food are priced with that in mind, of course."

"Wow!

Howcome the door out of the Golden Oak Library lead here?"

"When Milliways appears anywhere and anywhen, it appears as one might expect, behind a door! Any door which might normally lead to some other, more ordinary location, can instead lead to Milliways. It won't do so forever of course- or rather it will, for a certain sense of forever."

He winks. Additionally, two of his tentacles perform some kind of gesture. Perhaps this is body language for whichever kind of people this Bartender comes from.

"What sense of forever will it always lead here in?"

"Why, as long as you remain inside our establishment, it will lead back to your home. So, for you, it may last quite a long while. Quite a few people use Milliways to get important work done when they're running full-speed towards a deadline outside. Would you like something to imbibe?"

"So no matter how long we spend here, it'll be the same time when we go back?

"With a few exceptions, yes!"

"Hmm. Well, thanks for the information but I'm not thirsty at the moment."

She'll bring Gloss up to speed again then look for anyone who looks like they want to talk.

Quite a few patrons glance, but most are in conversations of their own. Only one stares in undisguised curiosity. He waves when he realizes he's been noticed.

Then one of the unicorns will approach him.

"Hi!"

"Oh, hello! I- you seem- my name is Satish."

He extends a hand and then retracts it, running it through his hair.

"I'm Rainbowstar. Are you new here? What's your dimension like?"

"I don't know how to describe it. It's different than here since I can't hear God, and no one really asks me to help them. I guess, relaxing?"

"What's God? What do animals ask you for help with at home?"

"You don't know what God is? That seems hard to miss...who kept civilization together through the early days? God created humans and kept human civilization growing to where it is today. They're the one who created advocate-scapegoats, like me. I help people by taking the blame for their sins."

"I think in my world different animals kept civilization together in different parts of the world. And what are sins?"

"I've never had to explain sins."

He thinks for a minute before answering.

"Sins are mistakes that damage society. Poor decisions made for stupid or selfish reasons which undermine the social fabric. Most people are allowed to sin a little, as long as they manage it well enough. Phliosopher-kings and noble-scholars can't sin, or the people would never be able to trust their leaders. It's a delicate balance."

“So, more-or less the opposite of Virtues? Treachery, cruelty, selfishness, and so on? I don’t think we have a way to make sure people don’t do those things, our Princesses were created with harmony magic but one of them still ended up betraying the other.

How does being an advocate-scapegoat work, I don't think we have taking-blame-for-things as a profession or a lifestyle let alone as a whole kind of animal?”

"Suppose someone struggles with the same sin often enough. They can be treachery and cruelty, but they can also be other things. Suppose someone eats meat, because it would too hard to go without. They come to an advocate-scapegoat, who takes responsibility for their failing. Then, they can remain part of the empire."

"I don't think anyone does things that way where we're from but I suppose I can see the logic. Our Princesses ultimately decide what to permit and what to forbid but they're only two horses in the country and they're not really accountable for those decisions. And mayors and lords make decisions more locally but they're basically just ordinary ponies

And your kind of animal is made specifically for that role? Do you know how you're different from other sorts of animal who can think about these sorts of decision?"

"I was wondering why you use the word animal like that. Are only some of the people in your world ponies? Advocate-scapegoats aren't made for our lifepath, we choose it."

"What are people? And didn't you say God created you?"

"In our world, we call all the kinds of things that eat and move animals. Humans are just one kind of animal, but what makes us unique is that we are the only kind that can think. We refer to animals that think as people, but currently there are no others. As far as God- some say they created us, but others say that he created animals and we are simply the only animals that learned to think."

"I mean, you said God created advocate-scapegoats specifically?

We have lots of sorts of animal who can think. Dunno if we have any that can't, 'though some are a lot better at it that others- how do you tell if something can't think or if it's just really bad at it?

But actually I was figuring you were like alicorns, who are ponies but are a special sort of pony that's created by magic instead of being born."

"Oh, well, of course God made the covenant. God gives us covenants to keep. The advocate-scapegoats keep to the newest covenant. I can't be sure which animals are just bad at thinking. Do you think it might be possible to detect this? Our only technique has been watching and listening."

"Hmm. Pretty sure you could make a mind-control spell that only worked on things that could think. There are definitely spells to change what something wants, can you have wanting without thinking?"

"My understanding is that most things which can move and breathe can want, but there could be ways of wanting that are too simple for thinking. What do you mean we you say 'magic' and 'spells'?"

He's not going to pick a fight over it; he isn't an enemy of those who might practice magic.

"Magic's... powers some animals have that don't work like normal physics, I guess? Except there are also inanimate objects that are magical, they're just rarer. And some kinds of animal have magic which can do different things but it takes complicated techniques to do most of them, and those techniques are called 'spells'. Ponies in general have magic where we get a mark on our flanks indicating something we're good at, and unicorns can do telekinesis and also learn spells to do with whatever our special talent is, and I'm also bonded to a magic gem representing loyalty that gives me really powerful magic I don't totally understand yet. I'd have assumed God would have had to use magic to create animals, right?

And you said you're an advocate-scapegoat because of a covenant? how does that work?"

"Not such a convenient translation feature, then. In the empire, we use the word which you're hearing as 'magic' to mean anything that goes against God, so our unnatural abilities aren't considered 'magic'. It that sounds arbitrary and artificial, that's because it it. The world revolves around it. What advocate-scapegoats can do comes from a promise we made to God; he gives us the power to act against nature."

"What did you promise? And what does it let you do?"

"As an advocate-scapegoat, I promised to bear the sins of others. In exchange, God gave me the ability to sin without breaking the other covenants. Sin endangers other covenants because it shows God that we can't be trusted."

"So that's the third covenant? What are the other two? Is people being exiled if they sin part of the covenants or is it separate?"

"There are three covenants that everyone in our empire holds: thou shalt not kill, thou shalt not steal, thou shalt not lie. Because no one in the empire breaks those covenants, we're protected from harsh natural conditions, we can grow healthful food, and we never forget. The rest are optional, but they're very tempting to those of us that like having the power to defy nature."

"And those benefits only apply if no-one in the empire has done those things, unless an advocate-scapegoat has taken responsibility for it? Are the benefits an area effect rather than attached to the particular people who keep the covenants?"

"God forgives sins as long as you repent, but not everyone repents. That's when we come in. Repentance is regretting the sin, and intending not to do it again. The benefits do apply to the area, not just the people, which is one of the benefits of having an empire."

"Yeah, I expect it's pretty hard for predators to intend never to kill again. What covenants are there besides those three and the advocate-scapegoat ones? And you mentioned other magic goes against God; what other sorts of magic does your world have and why doesn't God like it?"

"Hey."

"Ah, this is my sister Shadowstar. Shadow, Satish here was just telling me about his world; apparently only one of their species of animals can think at all and they have covenants with a powerful magical being called God; not killing in exchange from protection from harsh nature, not stealing in exchange for food growing better, not lying in exchange for perfect memory, and other ones that only some people have; Satish takes responsibility for other people doing stuff they're not meant to and in exchange gets leniency."

"The core covenants and the lifepath covenants clearly defy nature, but most people see them as acceptable because all that matters is what God thinks. Killing is magic, stealing is magic, and lying is magic."

"I wonder why the translation magic here's translating things that way. We have killing, lying, and theft but they don't seem to have anything in common with the things we call magic. But Princess Celestia does say friendship's a sort of magic, and that's not obviously any more like the things we normally call magic than stealing and so on are."

"'Anything ordinary people can't do which has outsized physical impacts on reality beyond just ordinary actions'. That's how I would summarize everything we call magic, even if I disagree with most about which things should count."

"But ordinary people can lie and steal, right?"

"Depends what you mean by ordinary. Raiders, carnivores, and liars must think their way is perfectly ordinary, since all them can do it, but none of us could without breaking our covenants. Let's try experimenting with this translation magic. Sin. Magic. Superstition. Do those sound like synonyms to you?"

"No. 'Sin' isn't a word we have. 'Magic' is stuff like unicorn spells and pegasus cloudwalking and the powers Harmony Bearers have when we invoke the Virtues. And according to Princess Celestia friendship is also a sort of magic but I'm not sure exactly what that means, I assume there's some technical definition I don't know. 'Superstition' is beliefs that aren't backed up by evidence?"

"Now we're making progress! Well, far be it from me to give your culture the concept of sin if you don't have it. Essentially, most forms of cultural deviance and disobedience of the covenants don't go over well. Magic refers to things which can't be done within Khshassa- anything unnatural, especially if it's impressive or impossible given natural human abilities. This includes raiding, pillaging, stealing, and murder. This includes slaughtering, hunting, fishing, or otherwise capturing and killing animals. This includes lying, misrepresenting your intent, keeping secrets, and telling fictional stories. Basically, everything fun. Superstition refers to anything people believe will make their lives better, besides following the covenants- obviously, that includes magic, since magic includes anything unnatural- including things outside the covenants. A bit circular, but that's why they're synonyms. Make sense?"

"You're not allowed to tell stories or keep secrets? You're not supposed to be creative about making your lives better?"

"Ordinary people aren't. As I've said, I've chosen to make myself an exception for the benefit of the community. I could tell whatever lies I liked, although I find that I'm quite bad at it, compared to foreign magicians."

"Does that system work okay for your species? It sounds like it would be horrible for me. I guess your species might need to keep secrets less than mine does, but I think all the species I know that can tell stories or be creative have members who'd be hurt by not being able to do those things and a lot of members who'd be hurt by no-one being able to do those things. I guess advocate-scapegoats can find the animals who need to tell stories and the animals who need to solve problems creatively and have them tell stories for everyone and solve everyone's problems? But why make that necessary?"

"It's not my favorite cultural hangup. There are humans who can lie, though, plenty of them. They're all outside Khshassa, where they can sin in peace. I admit, I do enjoy being one of the few in our empire who can lie. Anyone else who wants it can leave. Most don't. Are you lying about something right now?"

"A little bit, yes."

"That's a nice change. I suppose it would be rude to guess what you're lying about?"

He's going to try it anyway, though; he mentally reviews the conversation so far.

"I guess it might be. Normally the animals I worry will find out wouldn't care how I felt about that and the ones who care what I feel about it already know."