Sirzechs Lucifer

Sirzechs Lucifer, formerly known as Sirzechs Gremory, is the older brother of Rias Gremory. Known as the Crimson Satan, he is the leader of the Four Great Satans who rule the Underworld with the title of "Lucifer". He is also the husband of Grayfia Lucifuge and father of their son, Millicas Gremory.

Appearance
Sirzechs is handsome and young, having the appearance of a man in his early 20's with shoulder length crimson red hair and blue-green eyes, similar to Rias. In fact, Issei describes him as the male version of Rias.

In his true form, Sirzechs takes a form of the Power of Destruction in the shape of a human with crimson aura.

Personality
Sirzechs is shown to be kind and caring towards others and prefer to have things sorted out through talking instead of fighting. Despite being a Satan, Sirzechs has a very laid-back personality, preferring to do things at his own pace which his wife would usually punish him for. Sirzechs, however, does have a serious side to him which he has only revealed twice, during his fight against Creuserey Asmodeus and his confrontation with Hades. Sirzechs is considered as a siscon because of his deep love for his younger sister, Rias Gremory, and as an overprotective father.

History
Sirzechs was originally the intended heir of the House of Gremory. He is also the childhood friend and rival of Ajuka Beelzebub, both being extremely powerful. In the past there was a quarrel between the Satan faction, who wanted to continue the War against Angels and Fallen Angels, and the Anti-Satan faction that Sirzechs was part of. Sirzechs, at the time, was an ace of the Anti-Satan faction alongside Ajuka and was even called a Hero. The result of the quarrel was the fleeing of the Satan faction to the end of the Underworld, and the creation of the current Devil society. It was also during that time that Sirzechs met Grayfia and fell in love with her. The two of them eventually marry each other after the end of the conflict between the Old Satan Faction and the Anti Satan Faction.

The Red Dragon Emperor's Awakening
Sirzechs made his first appearance in Volume 2 during Rias' engagement party, where he indirectly (but purposely) helped break off her engagement with Riser Phenex.

Birth of the Breast Dragon Emperor
In Volume 4, Sirzechs went to the Kuoh Academy along with his father for Rias' class observation day. Later, he and Serafall Leviathan were sent as the representatives of the Devils during the peace talk between the three factions, which was invaded by the Khaos Brigade. Despite so, the peace talk ended without any serious problems, and the leaders of the Three Factions successfully signed a peace treaty.

In Volume 5, he and the rest of the Satans attended the opening ceremony for the Young Devils Gathering, asking each of them to speak out their dreams for the future and starts the Rating Game for the Young Devils Gathering by arranging a Rating Game between his sister, Rias, and Sona Sitri, Serafall's sister, handing a medal to Saji after the match for his excellent performance.

In Volume 6, Sirzechs appears in Rias and Diodora Astaroth's Rating Game, which had been interfered by Khaos Brigade's Old Satan Faction where he confronted one of the leaders of the Old Satan Faction, Creuserey Asmodeus, attempting to reason with him to no effect before being forced to fight and kill the latter.

The Heroic Oppai Dragon
In Volume 8, Sirzechs appears in the Hyoudou residence during his supposed meeting with the other Satans, informing Rias that she will be undergoing a ceremony at the Ruins of Connection. Later on, he, Grayfia, and the other Satans acted as the Satan Rangers during the engagement ceremony between Rias and Issei at the Ruins of Connection where he fought against Issei in the last trial and was able to overwhelm Issei with ease even after Issei used Rias' breasts as a power up.

In Volume 9, he and Azazel has a conversation on the Hero Faction, talking about how they are gathering Longinus and Balance Breaker users in their organization.

In Volume 10, he appears after Issei's battle with Sairaorg informing him about his promotion test to Middle-Class Devils.

In Volume 11, he revisits the Hyoudou Residence to get the confirmation of Issei, Akeno, and Yuuto for the middle-class promotion, telling Issei he can call Rias by her name even in front of him before once again telling him to call him brother, which caused him to be hit by Grayfia using a harisen, telling him that he is going overboard. He also arranges for Ravel to become Issei's manager.

In Volume 12, Sirzechs and Azazel went to the Realm of the Dead to confront Hades, the God of the Realm of the Dead, attempting to prevent Hades from making any moves on the Underworld. Sirzechs later reveals his "true form" to comply to Hades' demand but warns him that he is unhappy with what Hades did to his sister, Rias, and his brother-in-law, Issei, and assured him that should they fight, he would eliminate him without restraint or hesitation. Afterwards, he and Azazel discussed about the aftermath of the crisis as well as about "one", known as the individual, and the "circle", known as the group.

The Legend of Oppai Dragon and his Lively Companions
Sirzechs was seen at the end of Volume 17, talking with the captured Euclid, asking why Euclid did such actions and comments that Issei is a brother that he can be proud of which Euclid sarcastically apologizes that he couldn't do the same while calling Sirzechs naive.

Powers & Abilities
Power of Destruction (滅びの力, Horobi no Chikara): Sirzechs inherited the Power of Destruction from his mother. He has overwhelming mastery of his Power of Destruction that allows him eliminates anything it touches.
 * Ruin the Extinct (滅殺の魔弾(ルイン・ザ・エクスティンクト), Ruin za Ekusutinkuto): Sirzechs is able to form his Power of Destruction by focusing its power into numerous highly mobile small spheres able to eliminate things without a trace as well as circumvent the defenses of his target, resulting in minimal damage to the surroundings.
 * Human-Shaped Aura of Destruction (人型に浮かび上がる滅びのオーラ, Hitogata ni Ukabiagaru Horobi no Ōra): Sirzechs' true form. He can convert himself into the Power of Destruction that destroys everything regardless of his will. The full releasing of his powers caused an earthquake in the complete Realm of Dead. According to Azazel, Sirzechs compresses the Power of Destruction into a human shaped that releases demonic powers that are ten times more powerful than the original Lucifer. Although, Sirzechs is unable to fully control it as the Power of Destruction spreads without his command.

Immense Demonic Powers: He, along with Ajuka Beelzebub and Rizevim Livan Lucifer, is one of the three Devils who are considered Super Devils, with their powers and abilities far exceeding even that of the Four Original Satans.

Master Hand-to-Hand Combatant: Sirzechs is also very skilled in hand-to-hand combat easily overwhelming Issei another master hand-to-hand combatant in a fist fight.

Magic Talent: Sirzechs also inherited the Gremory magic talent from his father.

Transformation Magic: Sirzechs also appears to be proficient in using transformation magic as Okita mentioned that he met Sirzechs in the form of a black cat.

Trivia

 * In Funimation's subtitles, Sirzechs' name is erroneously misspelled as Sir Zechs.
 * Sirzechs' name is derived from the names of two characters from the Gundam TV series, Char Aznable of Mobile Suit Gundanm 0079 and Zechs Marquis of Mobile Suit Gundam Wing.
 * Sirzechs claimed in Volume 6 that he once dreamed of being a musician, which was fulfilled when he composed the Oppai Dragon song to deactivate Issei's Juggernaut Drive.
 * Sirzechs loves to play the role of "Satan Red" with the "Maou Squadron".
 * Sirzechs is one of the two known Devils to be placed among the ranks of the Top 10 "Strongest Beings in the World" along with Ajuka Beelzebub.
 * Sirzechs is the only person among the devils who was able to make a sacred creature into his servant.
 * Sirzechs is over two hundred years old, having reincarnated Souji Okita as his Knight in the late 1800s.