Reo Yun-seo

Reo Yun-seo, generally called Yun-seo after her disinheritance, was a Ju temancer credited with designing the first theoretical rune self-cycling system during her time in prison. She was also a serial killer, suspected of murdering more than 200 Kuan and Seprum soldiers during the siege of Guk and executed for the attempted assassination of Grey Hand Agrippina.

## Early Life

Reo Yun-seo was born to Reo Byeong-hun, Ryu Chae-yeong, and Park Eun-ji in Seong, a provincial capital in the kingdom of Ju. Her parents were all anti-Kuan dissidents who threw the support of their family name and wealth behind Eunju and Eun jiju in the period between Kuan occupation during the First and Second Spiral Wars. A triplet, she had two identical siblings: sibling Reo Yun-min and sister Reo Yun-seok. Reo Yun-seok became famous in her own right for helping design Ju's writing system.

At the age of three, Yun-seo lost her left eye to a hawk. Incensed, her mother called for the death of the Kuan falconer who had handled the bird, which the provincial governor, a person known to have Kuan sympathies and ancestry, rejected. A small mob, rallied by Ryu Chae-yeong and Park Eun-ji, killed the handler and led to the governor's resignation. This earned Yun-seo a nickname that stuck with her for the rest of her life: hawk eye. By all accounts, Yun-seo enjoyed the rumors that she could see the future through her missing eye and encouraged them during her time as a temancer.

Yun-seo was close to Yun-min their whole childhood and could often understand her sibling's needs when no one else could. Yun-min suffered from delusions much of their life, most frequently, the insistence that they were Eu Nok in human form, sent to the terrestrial realm to assist Yun-seo. They often spoke in tongues, wrote in illegible text, and disappeared for days or weeks at a time. When Yun-seo traveled to an estate outside Guk to begin an apprenticeship in temancy, Yun-min traveled with her.

## Temancy and Arrest

Yun-seo earned a place in the Hwangbo Laboratory after successfully arguing that missing one eye qualified her under the blind or low vision requirement. Her mentor, Ko Seul-ki, described Yun-seo as "sharp, fast, but difficult to guide." Yun-seo often snuck out during storms to climb the cliffs around the estate. She'd return, drenched, shivering, and delighted. In a letter to her sibling, she once described a storm as "the power of the spiral combined with the intelligence of of a human." Personification of weather events pervades her writings. A month later, she wondered, "If a human can plant a rune, why not a storm? Why not the rain, or the dew?"

Yun-min encouraged such questions, writing back, "Or, indeed, why not the spiral itself?" While Yun-min traveled back to their sister's house before Yun-seo could respond, the letter itself held some importance to Yun-seo, who saved it in a waterproof and locked box that remained unopened by Kuan spiromancers even a year after Yun-seo's death.

After graduating with tepid honors from the Hwangbo Laboratory, she started work as a consultant in temancy, helping farmers decide when to plant and guiding Makkadi caravans through the Forest. Though she offered many times, Yun-min refused to enter the Forest, even when it meant spending years apart from their sister.

When a Kuan-Seprum army arrived outside a newly-declared Fei kingdom, intent on taking it and reuniting Ju, Yun-seo offered them her services as a temancer, a move that cost her most of her friends and her and her sibling their family name. During the siege of Guk, she poisoned an estimated two hundred Seprum and Kuan soldiers and nearly assassinated Grey Hand Agrippina before fleeing camp. She was captured in 14 SE and imprisoned until her death, along with Yun-min.

## Keystone System

While in prison, Yun-seo posited the existence of runes that could cast and plant other runes, also called rune self-cycling. She designed the first prototype for a reflexive self-cycling system, which she called the keystone. Her sibling eventually smuggled her writings out of prison and had them stored in Guk's national library.

Her system required five rune or rune groups to function, none of which existed when she suggested the system:

1. Keystone
2. Eyes
3. Random adjustment maker (RAM)
4. Yecheug or another predictive rune
5. Tear-down cord

The most important was a central hub called a keystone, named after the stone at the top of an arch that, when removed, causes the entire arch to collapse. The keystone has the ability to cast and plant runes in the spiral, thanks to a casting / planting updater (CPU) that could interface with the spiral the same way a human mind could.

The keystone receives inputs from the real world through a complex system of pointers and proxies and mages on the outside who cast runes of measurement. Modern proponents of self-cycling believe systems could eventually function with little, if any, outside human assistance, but at the time, Yun-seo could not imagine runes 'perceiving' the world without a human mind somewhere in the mix. In her system, designed to predict the weather, Yun-seo specified that the eyes of they keystone would measure temperature, pressure, rain fall, and humidity.

The RAM randomly alters part of the predictive system's scripts. Depending on complexity, Yun-seo suggested it could potentially make dozens or hundreds of random updates and plant one rune for each. The keystone compares the predictions to the actual weather, observed by the eyes. Random changes that improve the efficacy are 'saved' in the keystone. Those that make the predictive power worse are discarded. In this way, she based her system off the theory of slow change.

The final part of her system was a tear-down cord, which automatically, safely, and immediately shut the system down in case of catastrophic failure. Yun-seo emphasized this part's importance, warning that any self-updating system could quickly spiral out of control.

### Difficulties

Yun-seo noted three key problems with her system:

* It was unclear whether runes *could* cast and plant themselves
* Randomly writing new scripts could quickly fill the spiral with hundreds of slightly different scripts, making it hard to navigate
* It could take millions of random changes over hundreds of years to create a more accurate model, assuming most changes were detrimental

At the time of her death, she held little faith in her own system, calling it "a fantasy to distract from real-life events, which, of late, have been mostly negative."

## Posthumous Re-Inheritance

The Reo family fell out of favor and power when the Kuan-Seprum army retook Ju in 12 SE. Yun-seo's parents were tried for treason and executed a little after her. When Kuan magistrates discovered Yun-min had illegally taken Yun-seo's papers from her prison, they ordered them put to death, though they committed suicide before their capture. When her husband's life was threatened, Reo Yun-seok repented of her family's crimes, swore fealty to the Empire, and agreed to send her husband to Aksai, where he joined the saj's guard.

Some present-day Reos, however, believe Yun-seo and Yun-min should be re-inherited and given back their family name for their scientific discoveries. Others argue that doing so is needlessly antagonistic, given she was a serial killer. Recent efforts by Eniac to dedicate their work to Yun-seo were blocked by a Seprum regent.