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 Satans who rule the Underworld with the title of "Lucifer". He is also the husband of Grayfia Lucifuge and father of their son, Milikas Gremory.

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

Personality
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.

History
Sirzechs was originally the intended heir of the House of Gremory. 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 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 Red Dragon Emperor's Awakening
Sirzechs made his first appearance in Volume 2 during Rias' engagement party, where he indirectly (but purposely) help 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 Chaos Brigade. Despite so, the peace talk ended without any serious problems, and the leaders of three factions successfully sign a peace treaty.

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

The Heroic Oppai Dragon
In Volume 12, Sirzechs and Azazel went to the Realm of the Dead to confront Hades, the God of the Realm of the Dead, in which he reveals his "true form" to comply to Hades' demand but warns him that should they fight he will terminate the latter.

Powers & Abilities
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 "Magical Projectiles of Annihilation". As stated by Azazel, the reason why Sirzechs was chosen as Satan is mainly due to his overwhelming ability to nullify magic.

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. According to Azazel, Sirzechs' demonic powers are ten times more powerful than the original Satan.

Trivia

 * Sirzechs is the only Devil to have mythological creatures in his peerage.
 * In Funimation's subtitles, Sirzechs' name is erroneously misspelled as Sir Zechs.