This door was supposed to lead to the hall closet with the cleaning supplies, but Bella doesn't see any good way to mop up spilled soup from the kitchen floor. "Extraplanar studies students," she mutters, stomping into the bar in her nice useful boots. If she takes notes on this place she can probably get extra credit somewhere for it. She goes up to the bar, and notes the lack of bartender. Maybe they stepped out for a minute.
"Magic-detecting spells don't detect it. Divine and arcane magic have intercompatibility that subtle arts doesn't have with either."
"That makes sense." And opens up a lot more questions. But there's one she should ask first. Taking a deep breath, and crossing her fingers that the answer won't be yes, she asks, "Is any of your magic transferable? Could someone from my plane learn it?"
"You have to be born with subtle arts, although there's some debate if you can get from 'no potential' to 'some potential' or just from 'no discernible potential' to 'discernible potential'. At home anybody can pick up magic if they're smart enough, but I don't know if your plane will allow it."
"Oh, thank you," she says, smiling. Magic is much more fun when she can just study it, instead of feeling obligated to use it. "Would you be willing to tell me more? I'm afraid I've been terribly rude, peppering you with questions...oh, would you like a coffee? This is a bar, after all, and I think I have some money." She starts rooting around in the pockets of her jeans.
"I don't m-" She blinks at the napkin. "Oh, huh, lucky us. I usually avoid coffee, though, it messes with my sleep patterns. Uh, hot chocolate?" She addresses this to the bar as though that's only a mildly odd thing to do and receives a large mug of hot chocolate. With marshmallows. "Thanks."
"Iced coffee, please. What sorts of things do subtle artists do? How much potential did you have?" She does a double take at the napkin. "Oh, is this bar run by some sort of computer? Or an invisible person?" She waves politely at the potential invisible alien.
"Subtle artists do mental perception and interaction, and some of us can also do telekinesis or pyrokinesis. I'm well above average for people with perceptible talent but hardly top percentile."
"Oh, congratulations on being above average. Can you do pyrokinesis? I do hydrokinesis, so that would be rather ironic." She notices the napkin. "Erm, thank you? Are you alive?" (This is hardly fair, she can barely talk to humans, how is she supposed to know what to say to a bar?)
I am a person, but not in the classical sense 'alive', says the bar.
"Teek...oh! Oh, telekinesis, it's an abbreviation. That must be quite helpful for everyday tasks." Her cat, meanwhile, is winding his way around her legs in a desperate plea for attention. She picks him up and places him on a barstool, then addresses the bar again. "So, if you're a person, could you please tell me just how you managed to appear outside my living room?"
The door leads to any door based on patterns or whims to which I am not privy. When you each open it, it will lead back to your respective worlds.
"I suppose it would be difficult. I can sympathize. It took Lord-knows-how-many hours of work to get my powers to do anything useful. At least you have professors who know what they're doing." Parvati may be a little jealous. "If you weren't a subtle artist, what other types of magic would you want to learn?"
"Arcane, probably. I can never bring myself to be very - positively interested in gods or nature, so that's the major divine magic out."
"How do you manage that, if you don't mind me asking?" she asks the bar. Her cat meows. "And does the 'first drink is free' rule apply only to people, or could I get my cat a treat?" She turns to Bella.
"Would you mind telling me more about arcane magic? And also...gods, plural?"
"I only know like high school level arcana," says Bella. "And that was a while ago. Do you only have one god active on your plane?"
"A bowl of milk, then, please," she says. "Hmm, perhaps it would be more productive to acquire some textbooks from your plane, instead of grilling you. Erm...bar-person, what would happen if I tried to go to her plane? Would I be able to get back? And yes, just the one god. Well, I believe there's just the one god, but people from other religions think differently. I wonder if any of the gods from your plane bear any similarities to mine. I've always been a bit frustrated that we can't prove his existence, but if people worship him on your plane, that would be rather strong evidence."
If she holds the door for you, you can enter her world, but you would not have any special advantage from there at obtaining a door on request, which most patrons cannot do.
"The major deity where I live is Khersis, but Mother Khaele also gets attention, and there are plenty of others who are just less locally popular. Yours is shy? ...The ones from the other religions are also shy?"
Then, Bella. "Do yours interact with you? That must be nice. Mine doesn't do that anymore, hence my inability to confirm that he exists. Same with all the others. Perhaps your plane is different in a significant way?" She vaguely recalls reading a book series in which God showed up in another world as a lion. A much more proactive lion.
Translations are supplied gratis.
"I'm... not going to comment on how nice it is."
"That is extremely convenient, thank you. I suppose that means it would be difficult for me to get ahold of magic textbooks from your world, as I don't speak the language or have any currency."
I can loan books, or sell them if you wish to take them home or mark them up.
"Oh, cool."
"How often do people find you? Is there some way to scientifically test when and where the doors tend to appear?"
I produce everything I offer spontaneously. Some people can find doors whenever they want them, or on demand some fraction of the time. Some people find me often and some rarely and some only once. I must assume some people never come here at all.
It's tempting to start reading some of them now, but it also seems a bit rude to start reading with Bella sitting right there.
"So, what do you like to do, besides magic?"
"I read, I show up to skirmish games, I'm not really very interesting."