Serendine Dikumenowlz Du Parthevia (セレンディーネ・ディクメンオウルズ・ドゥ・パルテビア, Serendīne Dikumenouruzu Du Parutebia) was the First Princess of the Parthevia Empire.
Serendine is a petite yet voluptuous young woman with a confident expression. She has pink eyes and light pink hair in a complex style: straight bangs, a purple headband, and several long braids, ending in metal rings. There are also two loops of hair framing her face. She usually wears a military uniform: a transparent tunic, a low-cut breast plate with a spider design, shoulder plates with a floral design, a purple cape, a metal thong, shin guards and boots that reach her thighs. She carries a sword at her waist.
After leaving Parthevia, Serendine cut her hair down to neck length in order to get money to survive.
Now her hair has grown almost to her shoulders and she wears a different uniform. Like her previous uniform, it comes with armour for her torso, forearms, and shoulders. Unlike her old uniform, however, she now wears a skirt and has discarded shin guards in favour of black leggings and a pair of boots.
Serendine seems to have an energetic personality and speaks with confidence. She's aware of her reputation as a tomboyish princess, but she doesn't seem to care; she's also proud of the fear she awakens on Parthevia's enemies. She has a familiar treatment with the people she's close to and cares about Drakon as if he were of her family.
Serendine can become brutally angry if someone speaks ill of her father the Emperor, injuring the person in question by herself and also threatening with torture, though it's unknown if she carries out her threats.
She is a prideful person and prefers to be treated more as a warrior than as a girl.
Due to the emotional and physical strain of the events prior, Seredine has become more prone to snapping at the people around her, is now easy to anger and blames Sinbad for not pledging his loyalty to the empire; going as far as to say that he was a "traitor" showing complete hatred and disgust for him. She even began taking her anger out on Drakon, treating him with something akin to disdain and giving him cold glares. She is shown in a flashback to have lost almost all of her pride for herself as a princess and can only try to survive day by day, by any means necessary. Seredine madly talks to Drakon, asking if the way she was living, trying to scrape up money in anything she could get her hands on, didn't make her any better than a prostitute.
After she comes to terms with herself and apologises to Sinbad for her behaviour she slowly regains her confident personality but becomes more humble and willing to help him on his in any way she could.
Dragul is thinking about the mission that is entrusted to him, and thinks aloud, saying that his brothers would never be assigned a mission of this kind. Serendine appears behind him and says that he shouldn't speak of such things so lightly inside the palace. She then greets him, saying that it's been awhile. When Dragul formally greets her, she says to call her just Seren, since it's shorter, and she addresses to him as Dragul Jr. Dragul asks her to call himself only Dragul since Jr was his childhood name. Serendine answers that he's too serious at times like these, and reminds him that when he was little he was a sweet little brother who followed her around like a duckling. Then she leaves that topic and says that she's heard that Dragul has been appointed the commander in the conquest corps. Dragul agrees, and says that, even if he's only the youngest son she treated him like one of her own family, and swears that he won't fail into the quest, because she will never do anything to soil her reputation. Serendine hits him on the head and says that she already has a terrible reputation as the Venomous Spider Princess of Parthevia, but that she likes this nickname, and thinks that suits her. Then, with a serious face, she says that if Dragul dies she won't forgive him, and takes her leave.
Serendine appears in Dragul's flashback when he's fighting against Sinbad inside the Dungeon. Serendine and Dragul's eldest brother, the Left General of Parthevia, Barbarossa, have been engaged and Dragul is formally congratulating them. Serendine is sitting next to Barbarossa, with a sad expression, and when she hears Dragul expressing his joy she becomes sadder, about to cry. She begins to say something but Barbarossa interrupts her, who thanks, Dragul in an emotionless way and says to the princess that he promises her a prosperous future of Parthevia. Dragul remains silent and Serendine's eyes fill up with tears.
After Sinbad and Drakon return from the Dungeon, she is seen staying with the army in the Contastia Harbor where Sinbad is said to be seen frequently. She orders her soldiers to capture Sinbad if they see him, and when her assistants tell her that there's no need for her presence, she answers that now they don't have many soldiers to mobilise, and she thinks that will make Sinbad pay for hurting Dragul. Then, some citizen begins to complain and insult the Emperor, which makes Serendine become furious and attacks the person who offended her father. She's about to punch the man again when Sinbad suddenly appears and stops her. Sinbad calls Serendine "Cute girl", much to her assistants' dismay, who quickly introduce Serendine as the first princess of Parthevia. Serendine confronts Sinbad and poisons him, but he manages to steal the antidotes from her and embarrasses Serendine by totally exposing her chest. Sinbad takes her as his hostage and boards his ship, but soon releases her when he begins his journey, calling her "cute girl" again.
Back in Partevia, Serendine is preparing for her wedding with Dragul's eldest brother, she thanks her attendants Sahel and Tamila, for being with her. As her handmaids talk about how the House of Dragul and the Partevia empire would now be closer, she becomes lost in thought. She thinks about how Barbarossa (or "the man in the iron mask") won't wait any longer for the wedding that she procrastinated over, she reminiscences of the time she was a soldier alongside Dragul she sadly says she was sorry to never have his back. She stated she had followed him when he entered the military academy up until now and is angered that he had not returned and had died in battle. As Serendine calls out Dragul as an "idiot" he falls down from the fireplace in her private quarters and the two stare at each other. She is first shocked at Dragul suddenly appearing and he explains how there was a secret passage that he used as a child, Serendine opens her arms and embraces Dragul; weeping happily and telling him how she was glad that he was not dead as she had presumed him to be.
Dragul tries to tell her something important, although he becomes flustered when he looks at Serendine, he tells her nothing is wrong with him when she asks why he was acting strangely. Dragul states that the clothing she wore made her appear "shining more than usual" while looking away in embarrassment, followed by Serendine laughing at his praise asking if he really thought that. She then smiles and holds her hand out to him, saying she was glad Dragul was still the same, commenting on his height and how his older brother Barbarossa would be happy to hear his little brother had survived saying they were holding a wedding ceremony here. Dragul looks at Serendine with fear at the mention of his older brother and when guards came bursting into Seredine's chambers by his brother's orders was to be executed, much to Serendine's disbelief and confusion. Dragul tells Serendine that his brother was just using her and tells her to put her faith in him; claiming that they had to leave Partevia.As Dragul takes Serendine and her handmaids through a secret passage to leave the castle, Serendine stops Dragul and tells him that she could not go with him, that she was a princess and that her abdicating her role would cause the crown to fall in power. Claiming that this would betray her father and her country she angrily tells Dragul she cannot forsake her duties and being the princess will become her life's meaning. When Dragul tries to convince her of the dangers, Serendine angrily calls Dragul's name which is then interrupted by Barbarossa. He tells Serendine he's happy she is safe and says they should return to the castle. Barbarossa grants Rotter, one of his four generals to "do as you please" with Serendine's handmaids and Dragul; she watches the fight ensue with horror.
Her face is full of joy when Dragul manages to beat Rotter, but becomes distressed when Barbarossa attacks and seemingly kills Dragul. She is outraged at Barbarossa angrily questioning whether he felt anything for his little brother whom he attacked. The persona she believed him to have was false and she tells him that she annuls their marriage and that she will be sure her father will hear about this. Barbarossa calmly tells her that her father is dead, and has been for a while. Barbarossa described to Serendine that her father had become ill on his last campaign and on the day of their wedding he had become so ill that he passed away. Realising that she was being used for the crown and that he killed her father, Serendine breaks down into tears as Barbarossa tells her as long as she obediently follows him, no one else would have to die. As Barbarossa forcefully tries to drag her away saying he'll be the emperor and she would be his empress, Serendine screams and says she'd never be with him. She starts screaming Dragul's name and manages to wake him.
The next time she is seen is when Dragul wakes up, although she is crying and apologises to Dragul, saying for her sake he had become one with his metal vessel, giving him the look of a dragon. Dragul however, said as long as it is to protect her, he'd always be happy. He pledged that she was his only master and that he would always be at her service. When he asked with the appearance he had now if she'd allow him to serve her, she replied with a smile and tears that she was the Venomous Spider Princess, and it was in her nature to cling.
During their travel, as they continue their struggle to escape from Barbarossa, Serendine and her group were constantly attacked by assassins. Because she felt her situation was hopeless, Drakon had tried to encourage her by reminding Serendine of her royal status and the fact that her brother was Barbarossa's prisoner. As they manage to cross the border and make it to the Reim Empire, Drakon had to stay on the outskirts of the cities that Serendine, and her handmaidens, were visiting. It was then, as they sold away any precious metals that had carried with them, Serendine had to experience hardships, for money and food, for the first time as she had to force herself to take any physical jobs, where she would work beyond the point of exhaustion, and had to sleep in stables; because of its unusual hair color, Serendine also cut some of her hair in order to sell it. As she was often asked, by random men, to be involved in prostitution did Serendine started to find it hard to believe that she was once a princess. The situation worsened as they were unable to leave Reim due to the country's strict supervision on ships and they financially can't support themselves for long-distance travels on land. It was then she started to resent Sinbad, believing he had the power to have prevented everything that Barbarossa had caused. Drakon, during his pillage on a passing caravan to get food, discovered information where he learned of the Sindria Trading Company of Napolia; this then leads him to take Serendine to Sinbad for help. As Sinbad and his company had returned from Artemyra, she is seen standing in the lobby, angrily asking Drakon why he had brought them to the Sindria Trading Company. Serendine yelled that she wouldn't approve of Sinbad, calling him her enemy and the man that humiliated her. She stated that appearing as she did was disgraceful, proclaiming her title in front of the others and saying she wouldn't let Sinbad get away with forgetting her. As Drakon had a friendly conversation with Sinbad on how he had not changed, Serendine glared at him whilst saying his name.
When Sinbad assured him that they could speak freely, Serendine spitefully told him that she had nothing to discuss with him as she stated that Parthevia would not have fallen into the hands of Barbarossa had Sinbad pledged his allegiance to the empire and served them, calling Sinbad selfish and using the power of a Djinn only for his own selfish ends. She continued her mad rant and branded Sinbad a "criminal" for turning on his country, betraying the empire, and so forth. As she said that all of what happened was Sinbad's fault, Drakon attempted to reason and calm her down, assuring her that Sinbad was not like that. However, she angrily tells Drakon to shut up, saying that if he allied with Sinbad he would become her enemy as well. At their wit's end, the two turned away from each other, both visibly stressed and tired. 
While Serendine is dead by this point, Sinbad has materialized a being of her character for his third trial and Zepar's dungeon, Trial of Souls and Puppetry. Her person Djinn Equip with Sinbad to challenge Aladdin to undertake Zepar's trial. 
When Sinbad instructs Alibaba on how to transfer the power of their Metal Vessel to a single person, he alludes to his experience when he inherited Zepar from Serendine. The process requires the donor(s) of the Metal Vessels to sacrifice their Rukh which the donor(s) will die in the process. 
Serendine is part of the Parthevian army and is feared by the enemies as the "Venomous Spider Princess of Parthevia". She is said to specialise in the use of underhanded strategy.
- Djinn Equip: In this form, Serendine takes the appearance of a small imp with dragon wings, a big belly, hooves, tail and three eyes. She is able to perform an incredibly loud scream able to "command" others into doing something.
- Hadeir (音魔法 Hadeīru)
Serendine is the Dungeon Capturer of Zepar, the Djinn of Spirit and Puppetry. In addition, he possesses the power of mind control. This Djinn dwells in the hilt of Serendine's sword.
Serendine has shown some skill in swordplay and can combine it with the handling of a dagger.
Her alias refers to her skill in using poisons. Serendine applies paralytic venom from giant desert spiders to her dagger and has been stated by her assistants that she has learned a hundred kinds of poisons from all over the world. Serendine always carries antidotes with her. The use of poison is a common thing in the Parthevian Royalty for self-defense.
She and Drakon have known each other since childhood. In Parthevia, Drakon was one of Serendine's servants and had a great loyalty to her. Serendine treats him familiarly and like a friend, regardless of the differences of their rank. She seems to care a lot of him and said that if Drakon died into the Dungeon she would never forgive him. She referred to him as her little brother. When she sees Darkon return she is surprised but overjoyed to see that he was alive. Also when Drakon is attacked by his older brother and seemingly dead, she cried out in rage towards her fiance and she would annul their marriage.
However, there are times when she was unable to hide her fears in regards to Drakon due do how he almost lost control of himself as he killed a large group of pursuers. Due to the amount of stress, from her travels, and how she partially felt betrayed when Drakon led the group to ask Sinbad, who she resents, for help did she began to temporarily treat Drakon more coldly. Their former friendship becoming increasingly uneasy and stressed, though she slowly begins to recover later as she eavesdrops in how trustworthy Sinbad is from his conversation with Drakon.
She claimed that she will get back at Sinbad for humiliating her and using her as a hostage. She also holds a grudge against him for hurting Drakon in the Dungeon.
When she meets Sinbad again, she is easily agitated in his presence and blames the fall of the empire to Sinbad; accusing him of using the power of a Djinn for his own selfish ends and not giving it to the empire. However, she later apologises to Sinbad for the way she acted and becomes more willing to aid him on his journey. She also begins to show concern for his actions and motivations while respecting his abilities from a distance.
Serendine became completely cognizant that she is unable to reclaim Parthevia by herself, where she was willing to use whatever expedient methods necessary. Thus, the princess was willing to make Sinbad her husband and allow him to have all the authoritative power, to rule Parthevia, while Serendine herself would be devalued to a mere political figurehead. She later tells Drakon that she hopes to help Sinbad become a revolutionary who can change the world while reclaiming Parthevia and atoning for her mistakes.
Serendine's Djinn. As Zepar chose Serendine as her King Vessel, the princess became touched with Zepar's solicitude, hoping that she will never be betrayed by her allies.
At first, she was uneasy being betrothed to Barbarossa, but she accepts it as part of her duty as princess. However, after seeing how coldly he treated his little brother, she said in a rage that she would cut off their marriage. He coldly reveals to her that her father, the king was now dead, and she had no choice but to marry him so he could be king. She refused and cried out for Drakon to help her who, after transforming, was able to help the princess and the two escape handmaidens.
Now, whens he talks to Sinbad, she view Barbarossa as a fiend taking over the Parthevian throne, but initially blames Sinbad for not turning his Djinn power over to the empire. She later comes to believe that it was her own weakness that let the Empire be taken over and has sworn to reclaim it and atone for her mistakes.
- Seren is a Turkish name, that means "(marine) yard, rank or post". In Welsh, her name can mean "star".