Amaryllis of Whitewood

Life

Childhood

Father had a Thinker's Blessing. Mother somewhat famous for sleeping around.
Strange medical condition resulted in not manifesting any obvious affinity for fire- this came to a head when she once burned her fingers as a toddler.
As a result of this, there was a lot less pressure on her. She could not inherit, and also would serve little use to continue the family line.
Quite well-travelled in general. Her parents were famously considered soft and foolish for this, as they'd mostly covered up her disability. Visited the Eideli empire before tensions really rose.
Traveled to the molten desert and partook in the glass-eating ritual. Probably the highest amount consumed by a single person since the creation of the ritual. Comatose for days and bedridden for weeks afterwards. It's not clear whether she actually just intended to kill herself here, but whatever the case, this resulted in an immense affinity for Fire. Watched over by a mirage dragon, who would appear to her on several occasions during her journeys in the desert.

Desert Adventures

"My name is Amaryllis, and I have 2 years to live."
Physicians are confused, and many agree that Amaryllis doesn't really have long left to live- perhaps a few years at most. At 16, she doesn't want to just sit around and wait to die; one of her childhood dreams was to see the world. Her parents end up obliging her- though technically firstborn, her lack of Fire affinity means an inability to inherit, sickliness only compounding this. They'd also rather their last memories of her be a healthy person setting off to fulfill their wish than wasting away slowly. Note that she leaves with a single bodyguard, along with access to her family's Abyssian Vault account. They don't really store much in the Vault compared to their own holdings, and are willing to give her free rein.
After thoroughly exploring notable landmarks in the midlands, she goes south to Eidel. Tensions between Eidel and the Midlands are in a lull, the border guard relatively accepting.
There, she hears rumors that those of the Molten Desert aren't born with an affinity for fire, instead developing it through a ritual. This catches her interest, and she makes it her goal to participate in one of these.
Organized glass-eating rituals only really take place around the Oasis, so she had a long journey ahead of her. Navigating the Molten Desert isn't easy, especially for an outsider unaware of the typical star-based orientation methods that natives use. One night, she takes shelter in a cave. Unknown to her, the resting place contains a passage leading all the way to the Great Caverns. A reacher comes through, sensing fresh meat, and she barely escapes with her life. Her long-term bodyguard isn't so lucky.
During the consumption ritual, Amaryllis ate so much glass that observers were worried that she might simply bleed to death on the spot. While she survived, she was comatose for days, and her voice never recovered past a scratchy whisper. Some say that they saw a mirage dragon watching over her tent as she rested.

Return

Some time later, Amaryllis returns, healthier than anybody would've expected. It's a shock, but not an unwelcome one. Her younger sister finds governance distasteful, and is glad to give up future responsibilities. Her parents were visibly embered at this point, though the drinking they'd taken up to cope with her supposed death had prolonged the process quite dramatically. Her return, ironically, sped their demise, as they chose to spend their remaining months sober enough to spend time with her.
Amaryllis takes her seat, and while some eyebrows are raised, the duels quiet any whispers quite effectively. Her glass manipulation allows her to leverage Fire affinity in a way that actually lets her hurt other Fire-aligned, wielding a tentacle of stormglass capable of constricting movement and denting steel in a manner reminiscent of how the Eideli utilize xiphaem. She's also happy to share her knowledge, although much of it goes over prospective students' heads- especially when she tries to express arcane concepts that the midlands don't have a vocabulary, or even framework of understanding, for. Whitewood, already dominant, gets another feather in their cap.

Death

She was unstoppable on the battlefield, so they killed her in her sleep. Eidel offered a lot of concessions to the next person in line for inheritance. Most notably, a binding oath to not push Eideli military forces further than the southernmost point of Whitewood. Post-death, her legend often portrays it as a noble sacrifice in order to secure the safety of her lands. In reality, she died messily; choking on blood beside a sister too terrified to finish the job cleanly.
The official explanation for her death was that she was performing forbidden soul experiments (technically true) and went too far. This actually has a bit more nuance to it than it initially seems- the assassination wasn't purely politically motivated. In desperation, Amaryllis dove deeper and deeper into soul manipulation and arcanism: by the midlands belief system, she was essentially committing the cardinal sin. Her murderer saw it as saving her from herself, with the added benefit of halting Eideli aggression. The rituals were seen as proof of how far she would be willing to go for her people, adding to her legend posthumously.
From a utilitarian standpoint, this was a reasonable move for the safety of the midlands. It just happened to backfire due to unforeseen consequences: not fifty years later would the heart of the empire be shattered by a war of gods. So Whitewood ended up stuck with the worst of both worlds- considered a traitor by neighbors, and without the backing of a foreign power. Five hundred years later, Eideli conquest would have been functionally impossible due to the entire populace having a minor Fire affinity, but at the time of Amaryllis' death, it was nowhere near ubiquitous enough to halt spindle assimilation.