He doesn't have enough familiarity with Earth mythology to even know what unicorns look like when they don't look like these plastic Barrayarans here.

"Other mythical creatures... griffins, pegasi? Mermaids, selkies?"

Pegasi yes but not on Barrayar, griffins yes but not on Barrayar, merfolk yes including on Barrayar, selkies yup not on Barrayar - "wow."

"I wonder why people don't mostly know about this, magic things are all over the place."

"It seems like it's very hard to find out by accident - Miles has been through every conceivable medical test and no one has ever discovered that he's a unicorn-or-merfolk-or-neither..."

"Obviously there is magic. But some people know, I don't know why they'd keep it so secret..."

"Also this is just a recurring mystery about Earths but - all of the other ones have the same mythology and none of them have the actual things -"

"None of them have any mythological things?"

"Aurum has vampires and Wish has magical girls and Revelation has angels and demons and fairies, but none of them have this kind of magic, we'd have noticed when we were resurrecting people."

"Weird."

"The conflict between the dragons and the sphinxes does seem to be a very secret one, but I'm not sure whether that's cause or effect of mythical creatures being secret in general."

"I bet we can find an explanation if we look through enough stuff."

"Can you get all the books a person has read, in case some of these dragons ever read books about dragons?"

"Nope. I can get the complete written works of your universe and search for references to dragons and sphinxes but you have a big universe, I'd need somewhere to put a really big computer and it'd still take a long time."

"Books published by dragons, narrowed down further by planet and date of publication if necessary?" she suggests after a moment's thought.

"That I can do. Same sort of data disk?"

She nods.

Now she has the complete published works of dragonkind. They take up several data disks.

"Simon will be overjoyed," she murmurs to herself. (Simon will also be understatedly terrified but she chooses not to share that part.)

Time to read things - "do you two want to divide up the reading since there are multiple disks?"

"Yeah."

Here's a reader, there's a reader, what have the dragons been publishing?

All kinds of random things, apparently dragons are just as likely as anyone else to write books on flying kites and baking pies and piloting jumpships and coming of age during the colonization of Escobar and octopuses. They even write fantasy books with dragons in them. Nika is the first to find a relevant work, and it refers to others, and soon they have a reasonably clear overview:

Dragons (sphinxes griffins etc.) are almost all turned human by a spell that originates with (traditionally) a magical medallion or (these days) a magical tattoo, and then passes on without either accessory to one's descendants. If you have a medallion/tattoo you can shapeshift; if you don't you're whatever shape you were when you were born. Some species have species magic. Dragons and sphinxes have the best species magic; antimagic at close near-touch range for dragons, fairly arbitrary high-oomph powers for sphinxes but if they don't think through all their own detail work they pass out. Some species can't do the medallion thing and have to live in hidden enclaves. Sphinxes and dragons don't like each other and have sort of divvied up the nexus. Barrayar was Isolated for the Time when most of this happened, but e.g. Beta Colony is considered a sphinx planet.

"I'm interested in finding out more about how these various magical powers work."

"There's probably a book on that somewhere."

There is! There are! Also there are books on runecasting which anybody can learn to do.