|“||H-Hyou...dou...kun...friend. Hyou...dou...kun...precious... I...want...protect...||”|
She is currently suffering from amnesia, but was taken in by Issei Hyoudou, and was welcomed with open arms by his family. To many beings, including the Old Satan Faction, she is the Princess of the Olden Gods (オルデン神々のプリンセス, Oruden kamigami no purinsesu), and the Future Queen of Urk (困らせるの将来の女王, Komara seru no shōrai no joō).
Senna is the only known wielder of Enkidu, the Imperial Family's most prized possession, since her ancestor, due to the weapon being sentient and conscious.
Senna is very young, being only 14 years old, and naturally has a small form. Her hair is short and messy, reaching down to her chin, and has small, round eyes and a heart-shaped face. She has golden hair and red eyes. Since she began living in the Hyoudou Residence, she normally wears a loose shirt with a white jacket and a gray skirt, though she refuses to wear shoes for whatever reason, instead opting for sandals.
While in her Heavenly King form, Senna's appearance matures greatly. Her hair grows longer, reaching past her shoulders and ending at her thighs, and develops red markings over her body. Her clothing also changes drastically, wearing a blue top that exposes the underside of her breasts, a golden bangle around her neck with a golden bracelet on her left wrist, and a bracer around her left bicep. She also wears golden greaves with a gold combat skirt with red fabric flowing from it. On her right shoulder is a golden pauldron, along with a gauntlet.
Not much is known about Senna's personality prior to losing her memories, other than that she was very kind and shy, yet also deathly terrified of other people, even if they were people she knew, likely stemming from the circumstances surrounding her birth. When she is discovered by Issei, she suffers from speech impairment, and is reclusive at first, but gradually warms up to others thanks to Issei. She is also very attached to him, as she once considered him a good person, despite being aware of his lecherous perversions. When questioned about it, Senna states that she doesn't care, because underneath that perversity is a good person. However, it stems more than simply that. Senna considers Issei to be precious to her, likely because he was the one who saved her, and gave her a place to stay.
|“||The King has delivered her judgement...the sentence is DEATH!||”|
–Senna, in Heavenly King form
Due to her lineage, Senna has access to a spiritual form known as the Heavenly King (天帝, Tentei), a power accessible to all members of the Urk Imperial Family. In this state, Senna's personality drastically changes. She becomes much more mature, being sophisticated and cold, giving off the impression of a "terrifying behemoth" waiting to be angered. Senna is arrogant and haughty, and looks down on others, referring to them as "lowly mongrels." She also gives off the feeling of authority, something which she holds above the heads of anyone she meets. While in this state, she demands that all lowly creatures bow before her and recognize her as their ruler, regardless of race. She also refers to herself in third person, and never by name, instead calling herself "King."
Strangely, none of this is even remotely shown when she is with Issei, or rather when she is alone with him. Rather, she becomes very shy and awkward, something which annoys her, as her thoughts openly show that she cares for Issei a great deal, far more than what her usual shy and reserved self let on. Her affection is very prominent, and wants Issei to look at her, and only her, wanting to be his "Goddess." She also becomes easily jealous when she catches him with one of the other girls, and even shows herself to be very possessive, practically threatening to kill Akeno if she even so much as came near him or tried to seduce him. Sadly, she becomes easily flustered whenever someone teases her about her apparent (and obvious) affection for the Red Dragon Emperor. Senna has also made it perfectly clear that she is vehemently against Issei's dream of having a harem, as she refuses to share him with anyone, believing that all other girls besides herself are unworthy of him.
Senna was born to some tragic and perverse circumstances. Her mother was the Princess of Urk prior to becoming impregnated with her. At that time, Urk was ruled by her grandparents. The King of Urk was said to be quite affectionate towards his family, and loved his daughter greatly. Unfortunately, this love brought forth an unforgivable sin that tore apart the royal family; he impregnated his own daughter, thus Senna's father was her own grandfather. Fearing for her life, Senna's mother fled Urk, instead living in quiet isolation, but she couldn't bring herself to kill the yet-born child inside of her womb. When she was four months pregnant, word reached her that her parents had died, and thus she was made Queen. Unfortunately, the subjects were well aware of what happened between Senna's mother and her father, which led to civil unrest about the "bastard child" that would be their princess.
These troubled times led to Senna's mother becoming very troubled and tired, even losing sleep because of it. Regardless, she did the best she could to rule over her kingdom. Several months later, Senna was born, and she was given the name "Tengoku," the Japanese name for heaven. Much to her surprise, Senna had resonated with Ea and Enkidu, the latter of which had not been used since the age of Gilgamesh's rule, evident by the red lines across her body. This showed that Senna was a true, pure-blooded descendant of the Oldest King, yet despite this fact, she was still not accepted by her people. For the majority of her life, she was viewed with scorn and hatred, never recognized as a true "princess." Her mother had also informed her of the nature behind her birth, but the Queen had never despised her for it, calling her "her precious child."
Due to the hostility towards Senna, the girl rarely ever left the castle. When she was six, she was beaten by a man who had pretended to be kind to her, and nearly proceeded to rape her, only to be killed by one of the guards who was nearby. Since then, Senna has refused to so much as set foot outside the castle after the incident, and is terrified of other people, with the exception of her own mother. Her only comfort was Ea, feeling as if she was drawn to it, and often held it close to her, feeling comforted by it's presence. In spite of her reclusive nature, her relationship with her mother never changed. She had also become quite close with a guard who was tasked with protecting her; the same guard who saved her from her attacker. The guard had become something of a 'older brother' figure to the young princess, as he would teach her swordplay and read her books about the outside world, as Urk was cut off from the modern day society due to the barrier Gilgamesh erected around it.
On the day of her fourteenth birthday, the guard escorted her out into the town, as her mother had requested that she be with her in order to calm the populace regarding the recent outbreak of the plague that had been ravaging the town for several years now. To ensure that no one would recognize her, the guard had Senna wear a cloak, and stuck close to her. However, in spite of her efforts, the Queen was unsuccessful in easing her subjects. The situation became even worse when an assassin, one who had become disgusted with the royal family since the previous king's affair with his own daughter, attacked the Queen. He had killed Senna's mother right before her eyes, forcing the Guard to defend her as the assassin set his eyes on her. The crowd had begun to rally behind him due to his slander and openly-preached resentment towards the royal family, blaming them as the cause of the plague due to that they had done nothing to try and stop it.
|“||You...you filthy mongrels! No, even that word alone cannot describe the filth that stands before the King! You have dared to raise your hands to your ruler?! Worse, you dare to try and kill your King?! For your traitorous actions...the King passes her judgement! The sentence...IS DEATH!!||”|
–Senna passing sentence on the people of Urk
What happened afterwards is completely unknown. Sometime after leaving the devastated kingdom of Urk, likely out of disgust or possible horror after reverting back to her normal form, Senna found herself in Japan, having breached the barrier Gilgamesh erected with Ea. The trauma of losing the two most important people in her life caused her to lose her memory, and her speech became impaired. At first, she lived off the streets, though she was found by Issei, who took pity on her and took her in. There, she was welcomed, and immediately was offered a place in their house. This act of kindness shook her greatly, moving her to tears, and has since been living with the Hyoudou family. She has also become very attached to her new guardian's son, considering him to be a precious friend, and wants to protect him. Another possible reason for this sudden attachment is due to the fact that Issei is nearly identical to the guard who cared for her, despite having lost her memories of him.
In spite of her frail-looking form, Senna is actually quite athletic, and very smart. She is easily leagues ahead of even the most prestigious mathematicians, and is also quite strong, capable of living furniture with one hand, or even lifting a car above her head with relative ease. She is also far more sturdy than the average human, as she can easily take a beating. Due to her lineage as a member of the Royal Family of Urk, Senna possesses high spiritual reserves, but has little to no knowledge on magecraft, as the guard who taught her knew nothing about magic, but has been receiving instruction from Akeno Himejima, quickly becoming adept in the art, albeit only skilled in the basics. She is also a master swordsman, as she was able to keep up, and even outmatch Kiba with a regular sword.
Senna also has a few abilities which are either exclusive to her, or to members of her family.
Heavenly King Form: A power accessed by all members of the Urkan Royal Family. As the successors and descendants of Gilgamesh, the Oldest King, members of his bloodline possess a great deal of spiritual power, far more so than the average human. By entering into a state of mind that is devoid of emotion, separating themselves from all manner of things and reaching a state of "enlightenment," the user can temporarily transcend to a higher plane, and gain greater power. This power can also change the user's mentality, as is the case with Senna. Senna is also a unique case, as she can access this form via emotional turmoil. The first time she used the Heavenly King form was due to witnessing the death of her 'older brother' figure and her mother, which triggered the transformation. She also used this power when Issei was about to be killed by Raynare; her overwhelming desire to save her triggered the transformation, allowing her to defeat Raynare easily.
Absolute Authority: A power unique to Senna. This power was said to be used by Gilgamesh, though whether or not this is true is unknown at present time. This power allows Senna to virtually command, or make anyone obey her commands, regardless of whether or not she is in her Heavenly King form or not. By exerting her "authority," she can make people follow her commands, so long as they are within reason. Subjects to this power have no memory of being controlled. When in Heavenly King form, the effects of this power are amplified, and can force even powerful beings, even those of the likes of Reapers; creatures who hold in their power to grant death to all living things, follow her will. Senna has shown that she has no control over this power, unfortunately.
Absolute King Form (絶対キングフォーム, Zettai Kingu): A power that is unique solely to Senna. The nature behind this power is unknown, other than it can only be accessed when Senna is synchronized with Issei while he is in Balance Break. Supposedly, according to Azazel and Ajuka Beelzebub, the Absolute King form is the equivalent, if not superior power, to that of a Longinus-class Sacred Gear.
Sword of Rupture, Ea (乖離剣・エア, Kairi Ken - Ea?) is the most powerful weapon ever forged, wielded by Senna's ancestor, Gilgamesh. Unlike all of his other nameless weapons that were able to be passed on to other wielders over the course of history, it is a sword only Gilgamesh possessed, a completely unique existence that can only be possessed by him, and later on descendants who were proven worthy of it, that is suited only for a ruler's use and makes them transcendent. Azazel comments that the nature of the sword becomes more absurd as he views its power. It can be used as a close combat slashing weapon wielded much like a regular sword, and even with its dull tip, it is able to pierce directly through Riser's chest and slowly grind at his vitals inside. It has an abnormal shape that doesn't match what would normally be classified as something specialized like a sword. It is something that was born before the appearance of the concept that the world calls a "sword", so it is not something that can truly be called a sword or have the shape of any known blade. While it has a grip, handguard, and is the same length as a longsword, the section that should contain a blade deviates from the normal form of an edged weapon. The "blade" itself and the tip of the sword, spun in a spiral shape, are dull. It has the shape of a cylindrical, drill-shaped pillar made up of three independently rotating segments engraved with crimson cuneiform lettering that spin slowly in alternating direction like querns, the middle segment spinning clockwise and the top and bottom segments spinning counterclockwise. The drill design was modeled after bedrock excavators used to drill underwater tunnels. Next to Enkidu, it was considered by Gilgamesh to be his most sacred treasure.
The sword itself is nameless, with "Ea" simply being the name that Gilgamesh chooses to call it, and it is described by Azazel as "the only sword that does not exist in this world." It is something that does not appear in any modern legends, crystallized during the Age of Gods at the beginning of the world. It is the primordial sword that is the actualization of the works of a god recorded before humanity came into being, and it is that which divided the formless into a distinct heaven and earth in ancient Mesopotamia. It is a divine construct created by a god unable to be replicated by any means be them man-made or supernaturally, and its status as a unique existence means it cannot be reproduced in any way. The names given to the sword and its ability by Gilgamesh are thought to be references to the Great God of earth and water, Ea, of the Mesopotamian and Babylonian myths and the Genesis Epic of the Babylonian myth, Enuma Elish.
Many wielders claimed that the sword "knows the truth" of the world where it once existed, and by using its power, it is able to bestow its knowledge upon others. As it is "The Sword That Cut the World Apart", they have come to call it “something that knows the hellish planet before genesis”, the planet's primordial form before heaven and earth were split, that was a land filled with naught but lava and gas and a hell of scorching heat and intense cold. Referring to it as hell, the wielders state that it is source of all legends of lands of the dead. The memory of the time before the existence of the planet, a place and time when organic existence had been impossible, is something possessed by all organisms, but it is no longer found in the imaginations or spoken memories of people. It is the first memory of life that is a genetically inherent and repressed knowledge which can only be shown to those looking upon the sword. The weapon "Slash Emperor" used by Ado Edem is also capable of showing a "Truth" similar in nature to that shown by Ea. In the desolate Land of Steel, it gives a glimpse of the blue sky before it was stained with blood.
'Enkidu: Chains of Heaven' (エンキドゥ：天国のチェーン, Enkido~u: Tengoku no chēn) is Gilgamesh's most prized possession after Ea, and also a sentient weapon. It is a chain named after his closest friend made to bind the gods so they cannot escape, making it one of the few anti-divine weapons that holds the concept of "reigning over the gods." The strength and durability of the chain grows stronger with the target having higher divinity, but is no more than a tough chain to a target without divinity like heavenly entities such as Michael or Azazel. When used against a regular human like Xenovia Quarta, she feels she has no chance of prying it off of her. Divine targets are completely held in place, allowing Senna to bind the "Bull of Heaven" that brought seven years of famine in Uruk. It does have some sort of limit, as even she is able to tell that the chain is not enough to completely bind Katarena Leviathan, who is empowered by the snake of Ophis. The weapon itself is embued with the soul of Enkidu, hence why it bears the name of Gilgamesh's closest friend.
- Senna's appearance is based on a young Eto Yoshimura, from Tokyo Ghoul.
- Most of Senna's weaponry is directly from the arsenal of Gilgamesh, from the Fate/stay night franchise.
- Senna is apparently a fan of the novel, Romance of the Three Kingdoms.
- Her likes include Issei, books, her mother, the unnamed 'older brother' guard, and sweet foods.
- Her dislikes include any girl close to Issei while she is in Heavenly King form, the people of Urk, and spicy foods.
- Senna is the youngest character to appear in DxD, being three years younger than Issei Hyoudou.