Most women of the Coiner line—eight in ten, say—lay eggs of impure gold, mingled with copper and silver in varying quantities. The more sex they have during their laying time when the urges are strongest, the more eggs they lay, and often the more valuable the eggs as well.
Some Coiner women lay silver eggs, and that used to be all they knew. Just an odd little quirk, that about a fifth of them lay slightly worse eggs. The eggs still had a little gold in them, and a substantial amount of copper, but they were silver enough that that's what they looked like to a casual inspection. Their laying times are often more intense, and they're quicker to arouse even when it's not that time of the month; they can get a little silly about sex.
Maybe one or two in a hundred, out of all the Coiner women, lay copper eggs. And that's where the trouble starts. A copper Coiner, once she has sex for the first time, is insatiable for the rest of her days; and copper Coiners are how the family discovered the true secret of the "worse" eggs, that every Coiner who lays less than gold has another womb gated behind the first, and another behind that, and so on; and the deeper you reach, the better the eggs. Silver Coiners have three, for silver and gold and platinum. Copper Coiners have five, copper silver gold platinum and emerald—and here Aunt Barla pauses, and takes Tanthe upstairs to show her a locked chest buried deep in the attic, filled with sparkling emerald eggs. Those were from Aunt Barla's own grandmother, who unlocked all five of her wombs in an encounter with a tentacle plant and then went to work at the Peach for the rest of her life because the only thing she cared about anymore was getting fucked as deep as possible. That's the curse part: the deeper you can go, the hornier you are at baseline and in potential, and the deeper you do go, the hornier you get. It's said, though nobody was exactly taking detailed statistics in the earlier generations, that each womb unlocked doubles your libido.
There are stories handed down over the generations, and a bigger chest locked even tighter and buried even deeper in the attic: copper Coiners with seven wombs, who make eggs of pure metal and flawless gemstone, copper silver gold platinum emerald sapphire diamond. There have only been a handful of them over the centuries, and they have, without exception, been even more insatiable than Great-Grandma Ferannith. Once they start, they don't stop. Great-Grandma Ferannith got unlucky; regular copper Coiners, whose copper eggs are alloyed with silver and gold, can pull themselves out of the spiral with luck and hard work and lead normal if horny lives. A Coiner with seven wombs can't, not in all the family's recorded history. One taste and they're gone. From the moment they first give in, let themselves get carried away just once and be penetrated sexually even in the ordinary way without opening a single womb, their laying time doesn't end until they die; and the more they give in, the stronger the urges get, in a terrible spiral of unending lust.
They test her first clutch of eggs, to make sure. Then they test them again, and then three more times. Pure copper. Not so much as a hint of another metal. She's a pure-copper Coiner, the most cursed of them all.
...she might have a chance, even so. Because, from her mother's line, she inherited psychic powers and an iron will to go with them. It's possible, barely, that she could survive having sex with her mind and will intact. If she was a mere ordinary copper, with only five wombs, she'd in all likelihood be fine.
But her family urges her not to try it. Mama looks ready to cry. They buy her sex toys that she can use alone, nothing that will reach deep enough to even tickle her first womb; inert toys aren't said to be able to trigger disaster, but they're not taking chances. As long as she's careful, as long as she manages and controls her urges, as long as she never ever has sex and so never starts down the path, she can grow up to inherit the inn like she's always known she would.
She makes it through her first laying time. She spends hours every day meditating, cutting into the time she usually spends helping her mother with the accounts. She stops helping the waitstaff in the tavern, because the occasional glance at her still-developing breasts is enough to have her running upstairs to her room to first take the edge off her urges and then meditate away what remains.
As the weeks pass until her second laying time, she makes Aunt Barla show her all the written records of pure-copper Coiners that the family has. She reads them over and over, learning everything she can about her condition. It turns out that the thing she already suspects about herself is a common thread among all of them: pure-copper Coiners can't masturbate to orgasm, they need a partner to achieve full release. Well, all the better, because an orgasm would be a serious risk. Tanthe satisfies herself in other ways. There's a lot of meditation involved, and carefully curating her nascent sexuality to respond well to safer things. She manages to coax herself into a deep and genuine enjoyment of slow gentle teasing touches, so that as her second laying time passes, and her third and her fourth and her fifth, she feels increasingly satisfied and fulfilled by her anorgasmic masturbation sessions. It gets easier every time, to content herself safely.
Her family gets her a Purity tattoo—it's not hard to afford, with Coiner money—to help her stay in control, and it's a breath of fresh air, helping her focus her meditation to recover faster and more cleanly from difficult moments. And... it's okay. It's hard, but it's okay. It'll be hard, but she'll be okay.
Probably. She hopes.