Sphinx

Sphinx (スピンクス) is a copy of Ryuzu Meyer, created in the Sanctuary by the Witch of Greed, Echidna. During the Demi-Human War, she participated in a campaign against the Kingdom of Lugnica and gained notoriety as the "Witch" who was a crucial member of the Demi-Human Alliance. She would later come to be secretly confined somewhere in the Barielle Barony by Leip Barielle, where she still remains in the present.

Appearance
Despite being around four hundred years old, Sphinx perpetually maintained the body of a girl roughly ten to twelve years of age. Her dark cyan eyes and charming face usually proffered an emotionless expression befitting of her mental state. As a half-elf, Sphinx's ears were distinctively pointed. She had long fluffy light-pink hair that curved outwards at its ends and trailed down to her hips. As a replica of Ryuzu Meyer, she was physically identical to the original and all of the other copies.

The only thing Sphinx wore over her body was a long white robe. Even her feet were left completely bare. Despite her innocent physical appearance, Sphinx radiated a massive aura of malignance and malintent that indicated her existence as abominable. Her demeanour of evil was so powerful that Sphinx had no way of hiding it.

Personality
According to Ryuzu Alma, the first few copies had broken personalities; this is shown when Sphinx had no problems with killing Libre Fermi, a fellow leader of the Demi-Human Alliance, just to have someone protect her. As she has a broken personality, she doesn't have complete emotions either and is unable to understand why Wilhelm tried to keep fighting even though he was injured, though things such as emotions intrigue her. She also has a habit of saying required (要 you) with a verb in accordance to certain things she mentions or sees, such as saying observation: required (要・観察 you: kansatsu) when observing Valga Cromwell's actions.

History
Ryuzu Meyer was a young half-elven girl around twelve years of age that became indebted to the Witch of Greed Echidna. The Witch, with Ryuzu's permission, began experimenting on Meyer in a secret laboratory. Echidna sought to unlock immortality by cloning Meyer and transferring her consciousness to the copy, meaning she could live forever via a long line of copies. She was able to create the first five copies of Ryuzu, the first of which she decided to transfer her consciousness into. However, the quantity of information contained within Echidna's soul proved too much for the copy to handle, resulting in an emotionless girl with a fractured mind who possessed a vast amount of magical knowledge and power, albeit not close to the level of Echidna herself. The girl left the laboratory and journeyed into the world with the hope of becoming complete.

For the next few centuries, the rogue copy, now known as Sphinx, travelled the world in relative obscurity. Around three hundred and fifty years later, Sphinx met Valga Cromwell and he led her to become involved with Demi-Human Alliance, a large insurrectionist force based within the Kingdom of Lugnica. The Alliance, made up entirely of the marginalized demi-human races, sought to reap the blood of their oppressors, starting a civil war as a result. Although her involvement was kept relatively secretive, Sphinx was considered to be Alliance's backbone, and she became the one of the three people most responsible for their successful advancements.

During the Demi-Human War, Sphinx set up testing grounds at Shamrock Valley and tested the efficacy of magic circles there at the behest of Valga. These magic circles exploded when triggered by a person walking over them much like a landmine. At some point in time, During the Battle of Castour Field, Sphinx's magic circles worked with brutal efficiency. Her usage of magic circles to lay waste to the Royal Army combined with an ancient spell used to create mindless undead soldiers from the deceased forces on both ends, she became key to the Demi-Human Alliance's victory. After encountering Wilhelm van Astrea, Grimm Fauzen, and Roswaal J Mathers, her existence became known to the Kingdom, and she was branded as a Witch.

Sphinx would soon get to work alongside Valga on a much more complex system of magic circles, and three years after the battle at Castour Field, the Battle of Aihiya Swamp would see the duo's efforts come to fruition. Knowing that the Royal Army would work to dispel any magic circle they came across, a hidden one across the entire swamp was created, being charged activated with the energy of the smaller circles after being destroyed. Under the magic circle's effects, humans were felt a heavier pressure as if they were underwater while demi-humans remained unaffected. The power became more potent on those were more adept in magic, costing many lives in the battle. Unfortunately for Sphinx, Roswaal did not hold any magical abilities and used physical combat, making the Witch withdraw to flee from Roswaal and her bodyguard, Carol Remendis. After finding Libre, who Valga needed regardless of his survival to advance the Alliance's cause, Sphinx used her magic to kill him, turning him into an undead puppet that covered her escape.

Not long after the battle, Sphinx, Valga, and the reanimated corpse of Libre enacted an attack on the Royal Castle by entering via one of its many hidden passageways. Sphinx was confronted by Grimm, Carol, and Roswaal. Carol successfully managed to cleave off her left arm, and not long afterwards, Libre cut her right arm off. Showing fear for the first time, Sphinx ran in shock and barely escaped death by entering another hidden passageway within the castle to escape to the sewers. Upon her escape attempt, she was confronted by Leip Barielle and captured. A short time later, Roswaal would come to question Leip about her whereabouts, to which he lied about the her death. Once Roswaal left satisfied with a necklace with a ring that Leip had taken from the Witch, he picked up Sphinx's body and would come to keep her alive for his own benefit.

Several months before the beginning of the main story, Leip and Sphinx would come to formulate a plan to gain control over Lugnica. After the beginning of the Royal Selection, Leip would aim to take away the will of his wife, Priscilla Barielle, who was a candidate to become the country's next King. By using Sphinx's powers to make her into a puppet, Leip would effectively rule the country if Priscilla won. However, after Leip was incapacitated by Al, this plan fell through. Some time later, she would attempt to take over Priscilla's body again by luring her to a trap. Using parasites that she had created, Sphinx would spread an infection from a waterwheel along a river in the Barielle Barony. However, this tactic would also come to fail when the infected waterwheel manager and host of the parasites' queen, Edda Rayfast, was burnt to ash by Priscilla. After this event, Sphinx began to deliberate on her next course of action and wait for a moment to strike again in the future.

Abilities
Parasite Creation: Sphinx has the ability to create parasites that take over a living target's body and turns them into "zombies". While their manner of creation is unknown, these creatures completely follow Sphinx's will and seek to create a "paradise" for her. They initially form in a host's body as a living tentacle-like appendage that is capable of physical movement. Upon taking control of a host's body, the host is killed, and the parasites are able to use the leftover brain's intellect and thought processes. While it is unknown if their process of taking over hosts is selective, they have only been observed to take over the bodies of adult males despite being able to nest themselves within women and children, with the exception of one female host who was established as the parasites' queen. Similarly to Sacrament of the Immortal King's effects, the zombies' bodies slowly decompose over time after being taken over. Though it is unknown if there is a limit on how many parasites can be created, it is possible for more than two thousand of them to exist at the same time, each loyal to Sphinx's desires.

Magic (魔導士 Madōshi): Sphinx has been shown to use a number of different magic spells for different elements like Yang, Fire, Water, and Earth resulting from the knowledge she inherited from Echidna, which makes her quite the potent mage.
 * Sacrament of the Immortal King (不死王の秘蹟 Fushiou no Hiseki): Sacrament of the Immortal King is an ancient and incredibly powerful spell, created by an unknown Witch ages ago. The spell, when cast correctly, will allow the user to reanimate corpses of the dead and make them do their bidding. Sadly, the technique to properly cast the spell has been long lost to time, and only an incomplete incantation exists which was transcribed in an old and withered book regarded as the most important heirloom of House Argyle. Originally, the spell was thought to be capable of fully reviving a dead person, and there are legends of the aforementioned Witch being supposedly capable of bringing back people exactly as they were before their demise. Effectively, the written chunks of the spell's full passage is incapable of producing anything more than walking corpses with no soul of their own, creating "corpse puppets" whose flesh slowly withers away and decomposes through time. To further limit the usefulness of this mostly-lost spell, a caster with an extremely rare natural affinity for the spell must be found in order to recreate even the most basic effects of this forbidden magic. As the version Sphinx used was incomplete, she was only able to reanimate corpses.
 * Magic Circles: Magic Circles are a type of geometric magic algorithm used to perform complex spells and rituals that can be drawn on objects or living beings. These can produce great kinds of effects, such as large-scale magic that completely alters the state of a battlefield, imbuing an individual with extreme power, or even temporarily cutting off Divine Protections by cutting an area off from the flow of Od Laguna. However, once Magic Circles are found drawn on the ground, their effects be nullified, so hiding them until activation is necessary. Since this is an ancient form of magic, very few people know about it and even fewer are capable of using it.
 * Jiwald (ジワルド): Using Yang magic, Sphinx was able to conjure and manipulate visible light into beams of scorching heat that laid waste to whatever object stood in its way. Offensive light magic was Sphinx's preferred method of combat. Like most spells, there were four levels of offensive light magic that increased in intensity and amount depending on the level. The most basic offensive light spell was "Jiwald" that allowed the caster to project a single beam of concentrated light out of a finger that was so fast that even the trained human eye could barely register it. Sphinx could also use the ultimate version of the Jiwald spell "Al Jiwald."
 * Al Jiwald (アル・ジワルド): The most powerful offensive spell in Sphinx's arsenal, consisted of a single ray of light projected from the Witch's entire palm. The spell was much faster and larger in scale than any of other Jiwald variation and was easily her most destructive, usually annihilating anything in its path. That being said, the soldier Grimm Fauzen was still able to deflect Al Jiwald with his shield.
 * Fire Magic: By superheating the air around her, Sphinx could produce and manipulate fire. During her first encounter with Roswaal, Sphinx attempted to incinerate Wilhelm Trias in a vortex of flames, though the master warrior abated the fire with his sword.
 * Flying Magic (飛行魔法 Hikou Mahou): Sphinx used flying magic, allowing her to float in the sky.

Trivia

 * Sphinx's first appearance in The Love Song of the Sword Devil predated the initial light novel appearances of the original Ryuzu Meyer and any of her other replicas by roughly ten months.
 * There are visual inconsistences between the description of Sphinx provided in The Love Song of the Sword Devil and the colored illustrations that accompanied it. Within the light novel, Sphinx's robe was referred to as white, yet a colored illustration displayed it as black. Additionally, the manga adaptation presented the robe as black.