For example:

Queen Danuhalmea of Mahlirou is getting to an age where if she doesn't produce an heir soon she's not going to. Her husband is not pleased with the lack of results.

Things are... not good... when King Lacaiphon is displeased.

She goes for a long walk in the woods late at night, and she meets a mysterious old woman, and she gets some advice. But she's so anxious that by the time she wakes up the next morning, she has entirely forgotten which colour of rose was for a boy and which for a girl.

It is very important to get that right. She must have a son. It would be intolerable to come all this way and then have only a girl to show for it. It doesn't bear thinking about. The old woman can come back and personally set fire to her bedcurtains and burn down the palace, and Danuhalmea won't spare a moment's regret as long as it ends in the King having a male heir nine months from now.

There are two roses beneath the upturned bowl she left in the garden, just as the mysterious old woman said there would be. She takes them both up to her bedchamber, and she sits and stares at them for an hour, trying and trying to remember which is the one she needs. Red for a boy, because he will grow up to be a warrior? Red for a girl, because she will grow up to be a woman? White for a girl, because it symbolizes innocence? White for a boy, because it symbolizes death? No matter how she tries, she can't recall.

Maybe - maybe she'll have twins, if she eats both. Twins would be bad but not nearly as bad as a girl alone. And maybe some other disaster will befall her or the kingdom, but so long as it's a disaster in the shape of a prince -

She eats both roses.

She has twins.

The sex of the elder child is difficult to determine, because the elder child comes out four feet long and covered in pebbly green scales, with blunt little claws at the ends of its scaly green arms and a tapering point at the end of its coily green tail, and absolutely no teeth in its tiny green head. It promptly bites the midwife and scrambles out the window.

The younger child is a girl.

When the Queen sees her, wrapped in a soft little blanket, she looks up at the midwife with an expression of hope. "Is it - a boy?"

The midwife shakes her head. "A girl," she says, "a beautiful baby girl. What will you name her?"

The Queen goes very still for a moment.

"Sarianiphera," she whispers; and then she bursts into tears, shrieking and sobbing with inconsolable grief.

The midwife tries to soothe her - "look, she's perfectly healthy, pretty little thing, the loveliest baby I've ever seen -"

The Queen lunges up off her bed and snatches a decorative axe off the wall. The midwife takes cover behind a side table, shielding the baby with her body.

"You - don't - understand," wails the Queen. "I can't let him have her, I can't -"

The axe comes crashing down on the table, splintering it in two. The Queen heaves it up again for another try as the midwife scrambles out of the way. But the Queen overbalances, and she falls into the wreck of the table, and the axe lands on top of her, and she lets out a horrible gurgling scream and then stops moving entirely.

The death of the Queen and the birth of the Princess are announced together that same afternoon. It was a difficult delivery, they say, and the Queen died bringing her daughter into the world. Closemouthed servants wrap the body in white linen and dispose of the axe and the table and scrub the blood from the floor. She is laid to rest with all due ceremony in the royal graveyard north of the city.

Little Sarianiphera grows up... quiet.

She is a polite and obedient girl, always attending her lessons without a word of complaint. Her calligraphy and embroidery are exquisite. She can host parties and recite poetry. By the time she is fourteen, she is already running the household in her mother's place. Everyone who meets her comes away with the impression that she is a wonderfully nice girl, if a bit shy. And, it becomes clearer and clearer as she grows, stunningly beautiful.

When the Princess turns sixteen, the king of Enniver sends a messenger asking to arrange a match with his younger son. King Lacaiphon refuses the first offer, and the second, and the king of Enniver desists. Offers come in from farther afield. King Lacaiphon refuses them all. The Princess turns seventeen. She is by this point renowned across the continent as the most beautiful princess in the world. Princes from distant kingdoms travel to Mahlirou to make their suit personally. Hardly a week goes by without another foreign dignitary arriving. The Princess turns eighteen.

Finally, her father accepts an offer. Or tries to.

He is discussing betrothal arrangements with an emissary when the doors to his throne room fling themselves wide and an enormous serpent slithers into the room, its scales clicking and scraping on the stone floor, its jaws agape to display large sharp teeth.

"My sister will have no husband until her brother has a wife," it announces.

The emissary looks at King Lacaiphon, and at the lindworm, and at the King again, and once more at the lindworm. Then he shakes his head and walks out of the room.

For some reason, perhaps out of sheer spite, the king becomes much more receptive to marriage proposals after that. Unfortunately, the marriage proposals have become much more scarce. The legendary beauty of Sarianiphera of Mahlirou is somewhat spoiled by the forty-foot-long reptile that slithers up out of seemingly nowhere every time her nuptial prospects are seriously discussed.

Legendary beauty will lead a lot of people to do stupid things, though, and eventually one of the foreign suitors brings his sister to offer to the lizard. The King accepts the proposal immediately. Wedding plans are drawn up. Foreign princess to marry lindworm within the week; foreign prince to marry princess two months later. Foreign princess does not seem entirely happy with this arrangement, but she doesn't speak any of the local languages well enough to voice an objection.

The day of the reptilian wedding arrives. The ceremony is small, awkward, and poorly attended. The foreign princess flatly refuses to follow her slithering husband to the bridal chamber afterward, until King Lacaiphon personally drags her there and locks her in.

When the maid opens the door the following morning, the lindworm is coiled up on the floor amid the bloody shreds of the princess's wedding gown, picking lace from between its teeth.

The foreign prince is not deterred. Unfortunately for him, neither is the lindworm.

"My sister will have no husband until her brother has a wife," the serpent hisses.

"We gave you one already," says King Lacaiphon. "Go away."

"My sister will have no husband until her brother has a wife."

The foreign prince eyes the enormous dragon with its enormous teeth and decides that maybe he's a little deterred after all. He expresses his regrets, assures King Lacaiphon that there will be no trouble over the sister, and goes home.

The next week, King Lacaiphon has the royal guard find a maiden of marriageable age and drag her to the palace. She is married to the lindworm and locked in a room with him all night, and in the morning there is nothing left of her but the bloodstained dress. He does it again the week after that. Despite the extreme discretion of the servants, rumours begin to circulate. The marriageable maidens of Dianaevo find faraway relatives to move in with, or unobjectionable neighbours to marry.

Unfortunately not all of them have those options. 

Altaia isn't actually one of those unlucky ones, but she observes that they exist. She observes that they're fed, once a week, to the lindworm, and no one has done anything about it effective enough even for her to have heard of their failure. 

And she doesn't really want to marry any of the eligible boys she knows. 

She goes out into the forest, looking for mushrooms and herbs that might, in sufficient quantity under a shift, be poisonous to kill a lindworm.

An old woman is walking along the path. Starlight gleams from her soft grey shawls, and tiny green sprouts poke out of the ground in the dents left by her walking-stick.

"My dear," she says to Altaia, "what troubles you so?"

...Whoah. Okay, advice from a mysterious old woman sounds like a way better plan than "try to guess how much poison it takes to kill a lindworm."

"The king is feeding unmarried women to a giant serpent and even if the only affect this had was that all women got married the moment they were old enough that would still be bad, but it's not, people are actually getting eaten, and if anyone else is trying to do anything about it I haven't found out, so I'm trying to find as much toxic fungus and vegetation as I can hide under a wedding dress so if I volunteer I'll at least be the last fatality."

"Would you like my advice?"

"I would love your advice."

"Then listen closely and do just as I say," says the mysterious old woman.

"The day after tomorrow, go to the palace and tell the guards you have come to marry the prince. Before the marriage ceremony, dress yourself in ten snow-white shifts beneath your gown. Ask that a tub of lye, a tub of milk, and as many birch rods as a man can carry be brought to your bridal chamber. If you have practical difficulties accomplishing any of these preparations, you will find the princess willing to offer you any reasonable assistance you ask for. After you are wed, when your husband orders you to shed the first shift, bid him to shed a skin first. He will ask you this nine times, and when you are left wearing one shift you must whip him with the rods, wash him in the lye, bathe him in the milk, wrap him in the discarded shifts, and hold him in your arms."

She nods seriously and repeats the instructions back to make sure she has them correctly.

The mysterious old woman smiles slightly and nods.

"You will find the results agreeable, provided you follow the instructions."

She pricks her finger with the knife she brought for cutting toxic things and writes down the instructions on the paper she brought to wrap toxic things in (fortunately neither has been used at all yet) in blood because not accidentally getting anything mixed up is way more important than the possibility of getting an infection.

The day after tomorrow she goes to the palace and tells the guards she has come to marry the prince.

The guards seem to find this a completely reasonable thing to say. They escort her to a room where she is told to wait for her wedding.

Huh. She was expecting more surprise.

She asks if she can talk to her future sister-in-law.

One of the guards doesn't acknowledge the request, but the other one says he'll pass it along. They leave her alone in her room.

Her future sister-in-law shows up about ten minutes later.

"Hi. I have mysterious old woman advice for how to solve our mutual problem."

"Go on."

"So I was going for a walk in the woods trying to see if I could find enough poisonous mushrooms to kill a lindworm with if smuggled under a wedding dress when I ran across an old woman with all the hallmarks of relevant mysteriousness, and she offered me advice. I have it written down, here," she says, retrieving the folded up blood-written paper from under her dress and offering it to the princess.

She reads it. She nods thoughtfully.

"Yes, I can make the necessary arrangements."

"Thanks." Sigh. "What a mess. I'm really glad I happened to have paper on me; the last thing this situation needs is more magical fucking up."

"You're right about that," she agrees.