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 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.

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.

Sirzechs is over two hundred years old, having reincarnated Souji Okita as his Knight in the late 1800s.

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 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 three factions successfully sign 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 arranges 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, he, Grayfia, and the other Satans acted as the Satan Rangers during the engagement ceremony between Rias and Issei at the Ruin of Connection where he fought against Issei in the last trial and was able to overwhelm Issei with ease even after Issei use 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 fight 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 set up 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 move 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 Rias and Issei and should they fight he will terminate the latter without hesitation.

Powers & Abilities
Sirzechs is a unique Devil due to the fact the he inherited the Gremory's magic talent from his father and the Power of Destruction from his mother. He is a wizard-technique type where he uses his Power of Destruction by focusing its power into numerous highly mobile small spheres to circumvent the defenses of his target, resulting in minimal damage to the surroundings. It is a style which requires high intellect and concentration, which he calls the "Ruin the Extinct" (滅殺の魔弾(ルイン・ザ・エクスティンクト) Ruin za Ekusutinkuto, lit. "Magical Bullets of Annihilation"). As stated by Azazel, the reason why Sirzechs was chosen as Satan is mainly due to his overwhelming mastery of his Power of Destruction that eliminates everything it touches.

In Volume 12, Sirzechs' true powers are revealed. He can convert himself into the Power of Destruction called the "Human-Shaped Power of Destruction" (人型に浮かび上がる滅びのオーラ) 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. He, along with Ajuka Beelzebub is one of the three Devils who are considered as Super Devils, with their abilities far exceeding even the Four Original Satans.

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

 * Sirzechs was once nearly killed by Grayfia Lucifuge for taking photos of her while she was sleeping.
 * In Funimation's subtitles, Sirzechs' name is erroneously misspelled as Sir Zechs.
 * Sirzechs claims in Volume 6 that he once dreamed of being a music composer, which was fulfilled when he composed the Oppai Dragon song to release Issei's Juggernaut Drive.
 * Sirzechs is one of the two known Devils to be placed among the ranks of the Top 10 "Strongest Beings in the World".
 * Sirzechs is one of two Satans who share a sister complex towards their younger sibling, the other being Serafall.
 * In both the light novel and manga, Lord Gremory and Lord Phenex discuss about the Welsh Dragon and the impending arrival of the Vanishing Dragon, while in the anime this conversation is held between him and his wife, Grayfia Lucifuge.