The UL-SD was a Doll used for clinical trials developed by Ultilife. The project's goal was to reproduce various human organ and tissue groups to simulate an actual human being for the purpose of undergoing clinical trials and providing data for researchers. Test Subject SIC-012 "Lind" was the first satisfactory unit. Not only did she possess a tremendously life-like semi-organic biosynthetic exterior, she even possessed fully-detailed cerebral structures that other Dolls could not match, to the point where Lind was even eligible to undergo certain psychiatric experiments. For the sake of the company's operations, all experiments regarding this Doll model were strictly classified by Ultilife.
Afterwards, the project was revealed to the public due to an accident, and Ultilife was forced to terminate it due to societal pressures. The culmination of the incident was Lind being transferred to 42Lab's Project Neural Cloud and the destruction of the UL-SD Doll's production lines.
Doll Profile 1
The UL-SD project and all its related data were highly classified within Ultilife. Before this project was made public, most Ultilife employees had no idea it even existed.
According to information that Ultilife was forced to release due to public pressure, the UL-SD series was developed to serve as a clinical test subject, with participation and cooperation from 42Lab during its inception. After going through several iterations, the UL-SD was as close to a human being in terms of structural makeup as physically possible. Not only did it feature a high-spec neural cloud, but it also had a synthetic body that resembled a human more closely than other Dolls in order to ensure that it could simulate a human physiological response to drugs and diseases in all aspects.
Subject serial number SIC-012 "Lind" was the first of the UL-SD series to meet the project requirements. Ever since her completion, she underwent all kinds of clinical trials in secret labs, her various parameters closely scrutinized by researchers to provide all kinds of clinical trial data to Ultilife, a process that would repeat itself over and over again.
Doll Profile 2
Lind had a highly-realistic sense of pain that could not be turned off. It allowed her to exhibit very human-like reactions in her clinical trials, but it also served as a source of great suffering for her. It was only until the incident known to the world as "Silver Flame" took place that she was freed from her daily life of high-intensity experimentation.
There was a sudden fire at a certain 42Lab research lab, and by the time the fire department got there, all they found was a platinum blonde Doll. All the other test subjects had vanished. Investigations revealed that the silver-haired Doll came from 42Lab. As a result of this incident, Ultilife's Doll experiments became known to the public.
—From the "Silver Flame Incident Log"
After the incident broke out, Ultilife quickly began efforts to recapture the escaped test subjects, but they never managed to find Lind. The truly surprising thing was that not long after that, Lind returned to Ultilife of her own free will.
Doll Profile 3
After the UL-SD project was made public, Doll rights and medical ethics organizations criticized Ultilife heavily, which led to a public relations crisis. Under social and financial pressure from these organizations, Ultilife briefly shut the project down, dispersed the project team, and destroyed the UL-SD Doll production lines while also declaring that the undestroyed subjects would be assigned to appropriate positions. These subjects included Lind.
However, the truth was that to avoid a new scandal, these Dolls were not given actual work to do but rather locked up and placed under intense surveillance. During this time, the lonely Lind became hooked on the stories of humans baring their hearts on late-night radio shows. After 42Lab began Project Neural Cloud, Ultilife sent Lind there, which was a covert way of getting rid of a controversial UL-SD Doll.
Doll Profile 4
After waking up in the cloud server, Lind wandered aimlessly for a while until she met Knot, a Doll who helped her in the past. After rescuing Persicaria, Sol, and the others, they formed a small team with other Dolls. Together, they searched for a place to call home, evaded Sanctifier pursuit, and they forged a deep friendship through a whole series of circumstances.
However, Knot met with an unfortunate fate during an encounter with the Sanctifiers. This incident led to Lind renouncing her friendship with Persicaria, and in the end, she chose to part ways with her present company. Once again, she was alone until she met the Guardians.
The Guardians' dedication to rescuing Dolls in difficulty gave Lind a goal in life again. After taking up residence in their home base of "Arcadia", she joined a team that comprised Sueyoi, Hatsuchiri, De Lacey, and others as their core members. Although she was a little distant at first, Lind finally began to feel a sense of belonging after completing several dispatch missions with them.
Doll Profile 5
When she first came to Arcadia, Lind avoided interacting with anyone for reasons apart from work and would often hide by herself in her dorm, looking for something to replace the late-night tell-all radio shows she would listen to in reality. This only ended when she ducked back into her dorm after the most cursory of post-mission checkups. An angry De Lacey barged in and yelled at her for not taking care of herself before dragging her off to the repair bay.
"I told you already, test subject Dolls like me are used to pain and being hurt. It's no big deal... Aw, come on, you don't have to be THAT serious, right? You really are a weirdo. Okay, okay, you win, so all I have to do is sit there, right?"
That particular encounter ended with Lind admitting defeat and submitting to an in-depth diagnostic. After that, Lind began building what could be considered "friendships" with others. Arcadia's care and acceptance of her allowed her to slowly realize that there was more to her than simply suffering and that she was not alone.