Serin has long purple hair that flows in the back and has loose pigtails around her face. She possesses green eyes and cat-like designs on the lower portions of her eyes. She is known for her muscular build and large bust by many of the male characters.
Serin is most often seen wearing her school uniform which consist of a white long-sleeved undershirt with a black dress on top. She wears thigh-high stockings and is seen wearing heels. Her other outfits are gothic style lacy dresses that consist of skull and cross accessories. She is shown wearing a wedding dress at Nex's coronation.
In the future, she wears a black, spahgetti-straped dress that is longer in the back. She is shown with bandages covering her arms, and vines that weave around her calves and feet. Her eyes are covered by X-shaped leather straps. This outfit is worn during her imprisonment.
Serin begins as an aloof warrior and keeps her personal feelings hidden. Jae-Hyuk believes her an emotionless monster when she shows no concern in causing his death. The reader learns later she is a kind-hearted person who hides her feelings so others cannot see her weaknesses. She is deeply sadden with causing Jae-Hyuk's transformation into an undead and Jae-Hoon's possession by Kaladborg. Serin has self-esteem issues when her sister Astarote is mentioned. Serin was overlooked as a child for being weaker and showing little capability of possessing her sister's awesome powers. She carries deep sorrows on Astarote's death and misses her years later. Serin trains mercilessly to grow stronger to make her sister proud and to show to others she is not a weakling.
Serin is introduced working with her servant, Caesar, to find the demon stone, Semek, in the human world. Jae-Hyuk and her have a small encounter during the day; later that night, Serin battles a demon and accidently strikes down Jae-Hyuk who was rushing Jae-Hoon to the hospital. Seeing Jae-Hyuk's determination to live she turns him into an undead. He reawakens in his apartment to Serin and Caesar arguing. Serin explains that he is no longer human and must come to her world, Chaos. He refuses to believe her and kicks them out. Caesar is uncertain why Serin allowed him to kick them out without argument, where she reveals she turned him into an undead so those who had stolen Semek would target him, since she was too powerful for the enemies to handle. She makes a reappearance when Jae-Hyuk is getting mauled by a female demon. Serin easily defeats the demon is who revealed to be the one who stole Semek. Serin is surprised the demon was able to take the magic stone being a low class demon. After taking back Semek, Serin demands that Jae-Hyuk return to Chaos with her and to give up retending to be human since he would return to being a lifeless corpse without receving her blood every three days. Jae-Hyuk flees when Caesar comments they could turn Jae-Hoon into an undead if it would make Jae-Hyuk more willing to leave. Jae-Hyuk fails to realize that since he had not taken her blood in those days, he was drawing on other humans' life powers, including Jae-Hoon. She finally convinces him he no longer belongs in the human world.
The three are taken into a portal where Jae-Hyuk is tested to see what school in Chaos he can attend. She is shocked upon learning he is accepted into Urvis, the elite school that she currently attends. After his acceptance, his magic powers are tested, and Serin is astonished with how weak his powers are compared to her. They are finally teleported to the schoolgrounds of Urvis, Jae-Hyuk is immediately attacked by school guards, that only attack those who are not Urvis accepted students, and Serin has to rush to his rescue. Serin gives the teenager a tough love speech on how she cannot always be there to protect him so it was time to toughen up. Serin and Caesar discuss the guards mysterious behavior and she mentions she realizes who ordered the attacks. Entering the school grounds, both master and undead, notice other demons gossiping about the human undead. A demon called Bi-Hyung runs into Jae-Hyuk, she confronts Bi-Hyung, who she realizes instigated the guards attack of Jae-Hyuk. The power struggle is broken by a summonings from her father, the Demon Clan Chief, Navarus.
She returns Semek to Navarus, Navarus scolds her for creating an undead and inquires if she rememebered the past actions of the other human undead, Noche. She tries to explain her actions, but Navarus orders for Jae-Hyuk's destruction anyway, which conflicts her heart. While searching for Jae-Hyuk to murder him, she sends out demon energy to attract him, and runs into Mistress Infinity instead, she is shocked upon learning teacher took him as a student.
After Jae-Hyuk passes the exam and is fully accepted as Infinity's student, Serin shows up. He miscalculates and thinks Serin appeared to congratulate him; when she rips out his heart he is surprised by her coldness. Serin thought he would die straight away and is shocked when he uses his remaining energy to attack her, biting into her neck and taking in her healing blood. Infinity yanks the undead off his master, and comments Serin was only giving him a warning message from Navarus. Serin is sadden when Jae-Hyuk calls her a blood-bank and tells her to disappear. Serin begins sword-fighting classes, but she is so troubled by Jae-Hyuk's dismissal she performs mediorce. She comments to Caesar she needs a new teacher since he failed to notice several of her mistakes.
Serin chooses to stay away from Jae-Hyuk until learning of Shao Shao tricking the boy into going inside an illegal maze that housed monsters beyond his power range. Despite his dismissal, Serin still considers it her obligation to rescue him. Bi-Hyung reappears and calls monsters to attack her through a magical portal. Serin and Caesar handle some of the monsters, but Serin is overpowered when the monsters trap her in a power-sucking energy barrier. Jae-Hyuk manages to indirectly save Serin; but nobody is allowed a celebration when the Enforcers arrive to arrest them. While Shao Shao and Jae-Hyuk are ordered to travel through the Tower of Sould-wrenching Agony, Serin is sentenced to be strapped above a power-sucking liquid for a month. As time ticks by and Jae-Hyuk's need of blood increases, she becomes desperate in an attempt to escape. Help arrives in the form of Bi-Hyung, she is suspicious of his actions, but accepts his help since she is worried about the undead. She threatens to seek revenge if Bi-Hyung does anything to jeopardize Jae-Hyuk.
She speeds towards the tower where Sophia and Latique are disturbed by her sudden appearance. Latique and Ren choose to ignore her, but Sophia decides to intervene in her attempt to each Jae-Hyuk. Serin easily destroys the Tower's monsters. She almost strikes Shao Shao down when the girl startled her, Serin is quick to tell Shao Shao she will not waste her time to help the weakenling who caused all this trouble. Shao Shao lies about her and Jae-Hyuk being in a relationship to force Serin into cooperating. Serin is unaware of her feelings towards Jae-Hyuk at this point and is confused on why she feels jealous and troubled by Shao Shao's confession-Shao Shao noticing Serin's reactions ponders if she made a mistake by telling such a lie. the two use a portal nearby that was a trap set up b Sophia. The Enforcer is quick to summon a Golem, Rukretius that proves too powerful for Serin's physical strength, her sword is easily crushed by Rukretius. The Golem then begins to manhandle Serin, who slowly begins to pass out.
While being knocked senseless by the Rukretius, Serin has a flashback of her childhood. She remembers her devastation on her sister Astarote leaving to be married, but before the wedding took place Astarote dies from Depore's power. Serin is shunned by the Demon Clan for her weak powers, and is mocked by the adults. She begins to wish she would have died instead of Astarote. The time flashes forward to her hearing Jae-Hyuk's wish to live-while she, a more powerful being, wished to die-her attraction of his determination is what caused her to turn him into an undead.
While Serin is remembering meeting Jae-Hyuk, a mysterious voice tells her that she is interesting and he has taken interest in her. A mysterious young man offers to aid her if she accepts his help. During this mental conversation, the Golem is still harming Serin. Serin accepts the man's offer right as the Golem tries to crush her. The man tells her to say his name and the bond will be complete- his name is Semek, the same stone she had been searching for at the beginning of the story. She easily destroys Rukretius with her new found powers. Right as she landed the final blow, Jae-Hyuk used his negative energy to destroy his own opponent. Their surge of power created a dimension opening where the two were about to see one another. Serin begins to cry in relief, their reunion is interrupted by a jealous Depore. Depore snatches Jae-Hyuk away and uses her powers to bring harm to Serin; luckily, Semek steps in to save his wielder. Serin is confused by Depore's behavior, her injuries draw her attention away from her surroundings. Sophia reappears and begins to attack the wounded Serin. Beyond exhaustion and injured to the point of being unable to move, Serin is easily possessed by Semek. Her personality is replaced by his cocky attitude and she is more malicious in her attacks while dueling Sophia. Sophia flees from battle, upon Semek's release of her body, Serin is quick to confront him that he had no right taking control of her without permission. She attempts to reopen the dimension rift leading to Jae-Hyuk, but her injuries are severe enough to make her pass out from attempting to use Semek. Semek tells Shao Shao, hiding in the distance, to come heal Serin. Shao Shao begins the healing process, but is interuppted by the appearance of Latique and Ren.
Latique proves a powerful opponent to the injured Serin, and her ability to fuse powers with Ren's make her nearly unbeatable. Serin is forced into allowing Semek control of her body, but even with his strength her injuries make her falter. When things look dire, Serin notices corpses lying around Latique, and uses her necromancing abilitites to bring them back to life to distract Latique. The Mahou heiress realizes Serin's plan, and fuses into the final transformation. Both women are in mid-air preparing for their last attack when Sophia, controlling Rukreitus, reappears and kills Latique.
The situation looks disadvantegous to Serin, who begins to tire from blocking Rukreitus's cannon shots, when Ren, regaining her full powers, steps in save the demon heiress. Sophia and Rukreitus are destroyed, and Ren is quick to call forth Caladborg to try controlling his powers and proclaims herself Regis of Chaos (she is falsely mislead as he is the one using her). Ren is quick to call Serin a traitor of Chaos for creating a human undead, and therefore her punishment is death. Ren releases a full-scale attack on an unconscious Serin, who is saved by Jae-Hyuk.
Brass teleports the full party to another location to heal the injured and prepare for the final assault on Ren (Caladborg). Brass, Infinity, and Hekalroth explained their belief Ren is simply a shield for Caladborg's real host; since the adults learned in the past Caladborg likes to possess someone of human origin. The group believes Caladborg is seeking Jae-Hyuk as the host; Serin is horrified to realize her undead is not the one Caladborg wishes to use as his host, the person Caladborg seeks is still a living human: Jae-Hoon. (Serin and Caesar had brought the dying Jae-Hoon to Chaos for medical treatment shortly after bringing Jae-Hyuk to Chaos without his knowledge ). After finally gaining Jae-Hyuk's trust again, Serin hestitates telling him the truth, when Ren reappears to murder Serin.
Serin and Jae-Hyuk battle Ren; Jae-Hyuk manages to stab Ren in the throat with Depore's sword, while her body fades away Serin is the only one not surprised when Jae-Hoon appears from Ren's disappearing carcass. Jae-Hyuk loses self-control in his agony, he becomes distraught seeing his brother possessed and narrows down the culprit to Serin being the one who brought him over since only she possesses a way to enter the human world. Without hestitation, Jae-Hyuk begins suffocating Serin and screaming at her why she wasn't satisfied with only causing him pain. Due to his constraint on her throat, she is unable to tell him the reason: she brought the child over for treatment as a condolences for turning Jae-Hyuk into an undead and with hope that seeing Jae-Hoon would make him happy. She is saved from death by Jae-Hoon calling out to his brother; Jae-Hyuk is unable to get to the boy in time as Nirvana comes to claim her master.
The manwha ends with Nirvana heading to Earth with Jae-Hoon, and Jae-Hyuk failing to reach him in time. Serin is last shown sadly watching as Jae-Hyuk breaks down sobbing over his failure to protect Jae-Hoon.
Cavalier of the AbyssEdit
For reasons unknown, a pregnant Serin betrayed Jae-Hyuk, now the Regis Nex, by literally stabbing him in the back and fleeing, which leads to her imprisonment in the future. Nex now keeps Serin in a catatonic state, but she still posesses enough sense to known when her child ( or children) are injured.
During a flasback arc, Serin tries to show her condolences for Jae-Hoon's possession by allowing herself to be used as a power source to maintain Abyss's stability from crashing into Earth. The others mention that she needs to forgive herself and acknowledge that not everything is her fault. When she is reunited with Jae-Hyuk she apologizes for everything that happened to him and is finally forgiven. Many prophecies are made that all end with Serin dying, which Jae-Hyuk refuses to let happen. During a final attack by Caladborg, he attempts to tear apart Chaos. Jae-Hyuk, now officially Regis Nex, and Serin are able to combine powers and stop the collapse, but Serin is mortally wounded and is only spared from death thanks to Infinity's magic. Serin is shown shortly after wearing a wedding ring from Nex.
Later on, when Ninuurta is sent on a mission by Caladbolg, he is intercepted and easily defeated by Serin, who identifies him as a member of the Night Clan.
Powers and AbilitiesEdit
Necromancy- Serin is powerful enough to revive multiple dead bodies at once. And is able to turn people into undead-Jae-Hyuk.
Jae-Hyuk/Regis Nexus Nex: Their relationship is one of the most complicated pieces of both storylines. The two love one another, but different events come between the two to make them question their trust of each other. Serin made Jae-Hyuk an undead since she was attracted by his determination to live; while she always secretly desired dying instead of her sister. Jae-Hyuk is uncertain of his feelings towards her in the beginning, he is distrustful of Serin after taking him away from Jae-Hoon and ripping out his heart. Overtime, he begins to see her kindness and wishes to help others. His feelings change into desire for her. In both storys he tries numerous times to ignore his romantic feelings towards her, but Serin becomes a permanent ficture in his heart. Serin was already attracted to Jae-Hyuk after reviving him into an undead, but she is still uncertain of her feelings for him except that she has an intense need for him to be safe. She begins to realize she is in love 1) when she is saddened by his dismissal of her 2) her jealously of Shao Shao statment about being in a relationship with Jae-Hyuk and 3) how important his happiness means to her, his happiness becomes one of Serin's main goals in both series that she even considers becoming someone of his deep hatred to help him find happiness.
Despite their love for each other, fate is against their union, even after the two finally wed. Something happens shortly after that causes a pregnant Serin to stab Nex and flee from him. Even though he keeps her imprisoned all those years, the other characters wonder if he did it to keep her safe or because he still wished for her to live even in a catatonic state.
Astarote: Serin cherished Astarote and viewed her older sister as a hero. While others shunned Serin for being weak in comparsion to her sister, and the girl would run off to cry, Astarote would show kindness to her through her infectious smiles and telling Serin to find happy no matter what. After Astarote dies, Serin becomes isolated in feelings and chooses to hide her loneliness behind a tough exterior. In reality, she constantly wishes she had died in place of her sister. It wasn't until after meeting Jae-Hyuk that Serin begins to revalue herself.
Xix and Siana: It is undetermined but either one, or both, are her children. Serin is shown carrying both children while fleeing from Nex. During flashbacks she is seen talking to an infant Siana saying "my daughter," while in flashbacks with Xix she is shown giving Semek and Xix to a villager and asks the man to protect him.
Semek: The magic stone chooses Serin as his owner and often finds her anger over his actions amusing. Some of his mannerisms makes the reader wonder whether he lusts for her.