"Tell them that their mother will be sorely missed by the academic community and it's perfectly understandable if they don't want to live here anymore but it would be nice if they could visit to reassure some botanists that they weren't kidnapped by some bizarre anti-botany conspiracy."

"I will let them know. There's - a couple more things complicating the picture there, they're not secret but they're so laughably implausible they make the snake seem entirely reasonable."

"Things that make the snake seem laughably plausible? You mean like people with unheard-of magic dropping on us from the stars to give us free things, drastically improve quality of life, and eventually end death?"

"Things that seem implausible even given that! Though I might be biased, I grew up with summoning."

"Try me."

"So summoning draws demons, angels, and fairies from the 'daeva realms', the worlds attached to ours - so to speak, we don't understand how it works at all, really - into our world, usually under specific conditions. You summon them and make an offer, if they accept it they do what you asked, you pay them, you send them home. 

Paying angels is easy - anything complicated, botanicals, electronics - and fairies is even easier - most consumer products. Paying demons is difficult."

"I can imagine," she murmurs.

"The - aboveboard - ways of doing it involve media recommendations, commissions for pieces of music or art, or live performances of same. This only gets you so far. And eventually someone hit on the idea that if there were daeva worlds and us maybe there were more than those, and they figured out a way to summon demons from other worlds. Demons who you could trade all our world's media, because they'd heard of none of it, demons who you could trade technology if they were from a world that was not as advanced as ours.

A while ago I needed a fleet of starships. I did not have anything on hand with which to pay for such a thing. I summoned a demon from a world that had not yet mastered travel faster than light, and I offered to trade her the knowledge for the ships, and she accepted - well, asked me to grab her twin sister as well, actually, her twin sister was an angel and they didn't get to see each other very often -"

The empress is missing a lot of context here but is following along well enough.

"You guys could trade them in dreamshaped magic items but summoning doesn't work here. Anyway. A few weeks after that I was notified by the demon I had summoned that she had found that a random doorway on our starship, which was currently mid-leap in deep space, opened to a interdimensional bar called Milliways. Where she had met Cam, who was from the same dimension as her to start with but had been summoned to a different universe with a Valinor, and an Endorë, and alternate universe versions of all the people I knew including me."

"We couldn't, dreamshaping doesn't do persistent magic items any more than it does persistent regular items," she corrects.

"I bet temporary magic items would still have some appeal. Anyhow. We investigated Milliways. Its most salient features are that while you are in it, time stops in the dimension you left from, time does not pass consistently between its parts, it is ridiculously powerful magic, and it has access to information about an indescribably large number of worlds.

We decided to close the door and hang out in Milliways until we had invented solutions to every single pressing problem in our home universe. There are some sufficiently bad that they should not be allowed to go on for even a short time longer than needed. We're still in the middle of that. We've been there about ten years. Well, I have, I don't know how long it's been for anyone else. Milliways doesn't let you do directed interdimensional travel, and we're close to having it on our own but not quite there yet. The only way to use Milliways for transit is for the bar to happen to put down a door somewhere, or to have someone who is currently inside the bar and who is able to open the door to a given universe - usually you can only open it to your universe of origin, but some people have a few candidates for that."

"A daeva could open the door to the world they were summoned from or the world they were summoned to, if they were on a summon?" she guesses.

"Yep. So it turns out that some worlds are recurring themes. There are for examples hundreds of millions of me, and hundreds of millions of my world of origin, which is a problem because my world of origin has some serious issues that - later in the trajectory they all follow - end up being disastrous. There're also alternate universe versions of people who don't come from the same worlds. We discovered this when we met an alternate universe version of my younger brother. It was thirty-one thousand years later, in his world, than it is in mine, and everyone had died horribly and then eventually been resurrected. 

...well, the Elves had been resurrected, the humans were presumed to be just dead."

"I'm sorry."

"The alternate universe version of my brother was sorrier, because he'd married a human. Thirty-one thousand years earlier. He'd met her in Valinor, where she'd been stranded by a random snake accident, and they'd gotten the Valar to make her unaging and they'd gotten married and they'd spent a few contentment-filled decades tromping around Valinor before everything went to pieces. She and her sister - who were alternate universe versions of my demon and her angel sister - died in the subsequent mess and he spent thirty thousand years moping, which is a thing Elves do."

"It was only a little more than a year ago."

"You see why I hesitated to say "ah, yes, I know an Idaia and Imliss Zevari-Lessnari."

She rubs her forehead. "Yes. But you said they're alive, earlier?"

"They were born again, thirty thousand years later, in the same world where they'd died. We don't know why. They were forty years old when we found that world and subsequently found them. Idaia and the alternate universe version of my brother joyfully reunited and have only very reluctantly left their rooms since. And then we checked and learned it'd only been one of your years, here..."

"...When you say she was forty, she wasn't psychologically forty, right, she was--herself--"

"...they get the memories back in dreams and I was not totally satisfied with that but the alternate universe version of Idaia, who is two hundred fifty, was and we deferred to her."

"That seems reasonable," she sighs. "I would have liked to meet them, to see if I could--figure anything out--but..."

"Well, now you have as much information as freeze-framing can get you, but you're still welcome to talk to them if you'd like."

"I would like that."