When she was fourteen, her warlock mark manifested for the first time: her face seemed to freeze over, rendering her devoid of facial expressions. Everyone who knew her noticed and feared her, apparently believing that she had turned into a Hannya demon or possessed by a gwisin. She was mobbed and buried alive. She was rescued from her coffin by the Crimson Hand, and the group helped her massacre her village in retaliation.
Shinyun had since become a devout member of the Crimson Hand. Because she didn't meet its original founder, Magnus Bane, Shinyun came at a time when the cult's direction was somewhat being controlled by Asmodeus, the Greater Demon that the cult worshipped. She took the cult's basic teachings to heart, particularly that they were all Asmodeus's children if they're proven worthy. Shinyun came to lead the cult, with the primary goal of summoning Asmodeus and ruling the world by his side.
Road to Rome
Shinyun planned to fully summon Asmodeus into the world in Rome. She was instructed by Asmodeus to bring with her Magnus as the final sacrifice needed to summon him.
Shinyun tracked Magnus down to Paris and intended to grab him at the local Shadow Market but was stopped by Magnus's boyfriend, the Shadowhunter Alec Lightwood, who chased her through the Market before she could escape. The group's efforts to take Magnus were once again foiled by Alec on the Orient Express. Realizing that she would need to get Magnus away from Alec, Shinyun changed their plan's course: she revealed herself to the pair and posed as a begrudged former member of Crimson Hand, pretending to be hunting them down for revenge, and joined them in their travels chasing down leads to the cult.
The group attended a party at Venice at the cult's old headquarters in search of Mori Shu, a former member of the cult who, according to Johnny Rook, offended Shinyun. Because Mori Shu would have given Magnus and Alec information, Shinyun killed him when the couple wasn't around. After the party was abruptly ended by a fight between two warlocks, Shinyun helped the two find the cult's secret Chamber beneath the palazzo. With the copy of the Red Scrolls of Magic she'd planted and the clue she added about going to Rome, the pair decided to travel to Rome next.
Alec decided to go to the Rome Institute shortly after they arrived, thus leaving Magnus alone with Shinyun. Shinyun pretended to have been in touch with a contact at a Downworlder bathhouse. While there, she joined Magnus in his bath and told him the true story of her past to make him more empathetic to her. She also took and disabled Magnus's phone then gave him a drink spiked with a potion that would make him lose his magic.
Shinyun soon brought him to the villa, the Crimson Hand's latest base, under the guise of it being the lead the informant had given her. Shinyun revealed her true nature to Magnus shortly after their arrival. Shinyun and the cult prepared Magnus for the ritual. Just as they were about to sacrifice Magnus to summon Asmodeus, the members of the cult, particularly Bernard who wanted to lead in her place, revealed that they intended to betray Shinyun, not wanting to be led by her strict rules and disregard for their desire for hedonistic pleasure along with the power.
The summoning of Asmodeus's spirit proceeded as planned but Shinyun was trapped within the pentagram with Magnus. When they were joined by Asmodeus, she learned that Magnus was in fact a true child of Asmodeus, infuriating her. Asmodeus froze her in place and Shinyun learned that Asmodeus intended for her be the sacrifice for his summoning. When Magnus refused, Asmodeus allowed her to move again and told her that he had chosen her. Shinyun tried to kill Asmodeus, but because he wasn't there in a corporeal form, the attempt failed. Asmodeus quickly forgave her and urged her to kill Magnus. Desperate for family and what she'd always seen as her glorious destiny, Shinyun attacked Magnus but was once again stopped by Alec.
When Magnus, with his magic restored, banished Asmodeus's projection, she and Magnus almost fell into the black pit that Asmodeus opened before he disappeared but were saved by the Shadowhunters who later arrested her. Shinyun remained quiet and noticed Magnus not telling the others about Asmodeus being his father. Because Alec noted Magnus's guilt and continued empathy for Shinyun, Alec decided to let her go while the others weren't around. Shinyun then returned to Korea and told Ragnor that she had a new plan, one that involves the eldest curses.
At some point after this, Shinyun used Ragnor as bait to get Sammael's attention as he had been looking for Ragnor to find him a realm. He sent her to retrieve the Svefnthorn, attune it to him, and use it on Ragnor. After doing so, she got permission to use it on herself which she did immediately.
In 2010, they moved their operations to Shanghai and even recruited a Shadowhunter to join their cause. Later on, they broke into Magnus's apartment to steal the Book of the White, hoping to use it to break the wards preventing Sammael from returning to Earth. While there, Shinyun stabbed Magnus with the Svefnthorn, though it was not approved by Sammael. She believed it to be a gift and a way to pay him back for his and Alec's act of mercy to her years prior. After he tracked them to Shanghai, she spoke with Magnus about power and gave him yet another wound from the thorn. She then followed him to the Shanghai Institute and attacked them all with an army of demons that she raised from Diyu.
The following day, Shinyun and Ragnor tried to opened a permanent Portal to Diyu in the Shanghai Shadow Market. Magnus and his friends fought the demons off until more Shadowhunters arrived. He then brought them all through the Portal so that he could close it from the inside. Shinyun let them travel the world alone for a while but soon grew annoyed with Sammael's torture on their companion, Simon Lewis. She offered to help the group rescue him in order to get Sammael back on track.
Instead he grew distracted once again when Ragnor was freed of the thorn and Sammael's will. He decided to focus on torturing this one group of humans and then to get Magnus to take the third thorn. Shinyun helped him force Magnus to agree by taking Alec hostage. However, Alec took the thorn himself and was able to use its power to free Magnus of the thorn. Shinyun became enraged that Magnus would throw away such a gift and that Sammael was so reliant on others. She deemed no one was powerful enough to lead her and that she would have to lead herself. She took the ball of magic that had been in Magnus for herself and transformed into a Greater Demon; with the Svefnthorn as her tail. She then fled and destroyed the realm.
Shinyun has brown eyes, thin lips, and straight, shoulder-length black hair. Her warlock mark was having a permanently blank, expressionless face.
As a Greater Demon, Shinyun no longer has an expressionless face. She is in fact twice her normal size with long limbs reminiscent of an insect's. She has dark blood-red wings and sharp fanged teeth. A long tail extends from her back which ends with the Svefnthorn.
- Immortality: As a warlock, Shinyun has been granted immortality. Physically, she does not age.
- Magic: Shinyun has access to magical powers that often manifest themselves as orange flames or sparks at her fingertips. She is capable of casting spells and performing summoning rituals.