Euclid Lucifuge is the younger brother of Grayfia Lucifuge, the uncle of Millicas Gremory and the brother-in-law of Sirzechs Lucifer. He was a member of Khaos Brigade's Qlippoth, being the leader of the Magician Faction Nilrem, and was considered as Rizevim Livan Lucifer's right arm.
Euclid is a young handsome looking man appearing in his early twenties with silver hair that is tied in a braided hairstyle. He wears a silver robe with detailed accessories.
Euclid is a calm and collective individual with a ruthless and manipulative side to him as well. A fanatic Lucifer loyalist, Euclid held utmost loyalty to the original Lucifer as the master of the Lucifuge Clan. Due to this loyalty, Euclid fully supported the original Lucifer's ambition and ideas of world domination as a member of the Old Satan Faction and became utterly enraged at his own sister for her refusal to support their master's ideology. Euclid's loyalty to Lucifer also extends to his son Rizevim Livan Lucifer, as it was Rizevim's heritage as a Lucifer that drove him to join Qlippoth and commit terrorism. Euclid also shares Rizevim's ideals of what a "Devil" should be, believing that it is their job to be evil, manipulative, brutal and ruthless. He even claims that his reason for joining Rizevim is solely for the sake of proving to other mythological factions that Devils are the most brutal species.
Euclid is shown to be completely obsessed with his sister Grayfia, going as far as to create a Replica of a Boosted Gear which is "Red" in order to become similar to Sirzechs, who is also "Red". His obsession with Grayfia is so extreme that he wanted to make Rossweisse his "sister" due to their similarities. This obsession, however, combined with his fanatic loyalty to the Satan Lucifer, also created tremendous disdain towards Grayfia for abandoning her role as a Lucifuge. He even went as far as to say that she 'went so low as to become a servant of the Gremory', referring to Grayfia's position as the Queen of Sirzechs who came from the Gremory clan.
In Volume 17, it was revealed that, for countless years, Euclid was emotionally torn between his love towards his sister and his personal dedication to his duties as a Lucifuge. Due to Grayfia defecting from the Old Satan Faction and betraying Lucifer, an act which Euclid considered to be atrocious as a member of the Lucifuge Clan, Euclid felt tremendous despair by his sister's betrayal and became immensely nihilistic, no longer taking interest and value in anything, only desiring to create and experience chaos. To this end, Euclid willingly followed and supported Rizevim in committing many atrocities, such as becoming a terrorist, causing tremendous damage and chaos to the Vampires' homeland, as well as launching an assault on Auros Academy, endangering the lives of innocent people and destroying parts of Auros Academy simply to spite Rias and Issei, showing utterly no remorse for his actions.
Like his sister, Euclid came from the noble House of Lucifuge and was also a part of the Old Satan Faction. In his youth, Euclid dearly loved his sister and admired Grayfia for her courage and strength as one of the strongest Devils of the Old Satan Faction. After Grayfia fell in love with Sirzechs and defected from the Old Satan Faction, effectively betraying the ideas of the Original Lucifer whom the Lucifuge Clan had sworn to loyally serve for generations, Euclid fell into despair and was completely heartbroken by his sister's betrayal. For centuries, Euclid was emotionally torn between strong familial love and intense anger toward Grayfia. When Euclid went missing after the Old Satan Faction lost to the Anti-Satan Faction, he was presumed dead by many, including his older sister. At some point in time, he met Rizevim and told him about Ophis' stolen power, the Holy Grail, the proof about the other world, and 666 (Trihexa).
Euclid first appears in Volume 14, where he helped the "Nilrem" and "Hexennacht" Magicians sneak into Issei's town. After Issei and the others successfully repel the Magicians from both groups, he teleports Issei and his friends to a factory which they built through magic in the Dimensional Gap, where he summoned Grendel to battle Issei. After Issei and Grendel fought for some time, Euclid ordered Grendel to stop, claiming that the experiment was a success and that they needed to head to Vali's place to assist them as they were having some trouble. Before leaving with Grendel, Euclid reveals his identity as Grayfia's brother to Issei and his friends, much to their surprise.
In Volume 16, Euclid was mentioned by Vali as one of those that blocked him on his way to the basement of the Tepes Castle. He later appears in front of Issei while Issei was exterminating the mass-produced Evil Dragons. Much to Issei's surprise, Euclid reveals a Boosted Gear Replica that he made after copying the Boosted Gear using the remains of Issei's previous body and the souls of famous Dragons. Euclid was initially able to overwhelm Issei easily, revealing that his strength was close to that of his sister. Issei, however, was able to counter-attack by using his newfound Reflect power. Euclid then retreats with Rizevim and Lilith after Rizevim orders it.
In Volume 17, Euclid appeared in Tokyo during Issei and Rossweisse's date much to their surprise. He later appeared in Auros, kidnapped Rossweisse, and was pursued by Issei and Rias. Euclid then revealed his goals before killing the magicians who were allied with them by having them self-destructing, effectively destroying parts of Auros Academy in the process. Euclid and Issei then had a rematch among themselves, which ended in Euclid's defeat and his replica's destruction after Issei used Longinus Smasher. He was then arrested by the Devils and imprisoned in a prison complex.
Later, Sirzechs came to interrogate Euclid for the reasons behind his actions, with Euclid replying that he simply had nothing while Sirzechs had Grayfia and apologizing that he couldn't become Sirzechs' pride like Issei. Sirzechs then asked Euclid if he was interested in the other world like Rizevim. Euclid answered that he simply wanted to experience 'chaos' and asks him what a 'Devil' is to him. Sirzechs answers that, while they have different values, they're similar to humans, creatures that are capable of both good and evil, causing Euclid to call him naive.
In Volume 18, it was stated that he was being interrogated by his sister Grayfia due to his request, as she harshly interrogated him for his actions and for information on Qlippoth, though Euclid seemed happy to see his sister again.
Power and AbilitiesEdit
Immense Demonic Power: Euclid has yet to demonstrate his full powers, but Azazel mentions that he was powerful enough to lead the Khaos Brigade himself. His aura is said to be similar enough to his sister Grayfia's, allowing him to get past the barriers protecting Kuoh Academy and let Stray Magicians in without detection. During his short battle against Issei, Euclid said that his strength is equal to that of his sister, Grayfia Lucifuge, who is said to have Satan-class powers. But in fact Euclid is weaker than Grayfia according to Issei's conclusion in Volume 17.
- Dragon Shot (魔力弾, Doragon Shotto): Issei's signature move that was copied by Euclid, along with the Replica Boosted Gear. Euclid fires a beam of energy by concentrated energy from his hand that's been enhanced by his Boosted Gear. Unlike Issei's Dragon Shot, Euclid's version is a mixture of red and silver.
Expert Magician : Euclid has shown to be highly proficient in magic, as he could bypass the barriers protecting Kuoh Academy and allow Stray Magicians to sneak in without detection. He is also skilled in other types of magic such as teleportation.
- Teleportation Magic: He can also use transportation magic, demonstrated when he summoned Grendel and sent him to Vali far away.
- Explosion Magic: Euclid can implant explosive spells inside the bodies of the Stray Magicians who infiltrated Auros Academy and set them to detonate when he needed.
Master Inventor: Through his own methods, Euclid was able to create a replica of a Longinus, something that not even Azazel, the leading expert in Sacred Gear research, could achieve as stated by Ddraig.
Flight: Being a Devil, Euclid can fly using his wings.
Boosted Gear Replica (Formerly): Euclid was able to create a replica of Boosted Gear by collecting information of the Red Dragon Emperor's soul and the Sacred Gear from Issei's original body left in the Dimensional Gap by using the Holy Grail. Unlike the original Boosted Gear, Euclid's Boosted Gear appears on the right hand with silver lining. While its potential is weaker than the original, Euclid demonstrated exceptional mastery of it to the point that he surpassed Issei, who uses the original Boosted Gear. Even Ddraig admitted Euclid can bring out the Red Dragon Emperor's power to the maximum. The Sacred Gear has a program that destroys itself if Euclid should ever be defeated, which it did after his loss to Issei in Volume 17.
- Boosted Gear Scale Mail: Euclid is able to use the Balance Breaker of the Boosted Gear by sacrificing the souls of several famous Dragons since he was unable to make a copy of Ddraig's soul. The armor looks like Issei's Scale Mail, albeit with slight variations. Like the Balance Breaker of the original Boosted Gear, Euclid can multiply his power any number of times he wishes, but at the cost of a large amount of his stamina and demonic powers. During his short fight with Issei Hyoudou in Volume 16, Euclid was able to overwhelm Issei with minimal effort in this form despite the fact that Issei was using his Cardinal Crimson Promotion.
- Euclid held hatred towards Sirzechs for his existence as a Super Devil, as well as having Grayfia's love and affection. Ironically, just like Sirzechs, Euclid has an immense sister complex.
- Euclid may have been named after the Greek mathematician Euclid of Alexandria due to both of them being master inventors.