Cult leader (in secret)
Sebastian Blood, also known as Brother Blood, is an alderman and undercover cult leader who rose to power following The Undertaking. He blames the Queen family for the destruction of the east sector of the Glades. In "Crucible" he is revealed to be an antagonist of Season 2.
In "Crucible", Sebastian helps Oliver to set up a "guns for money" fundraiser for people affected by both the earthquake, and gun violence in The Glades, to reduce the increased gang activity (due to "The Mayor" rising to power as a gang leader), but is shot at, along with the crowd during the event by "The Mayor"s' men.
After The Mayor is arrested, a corrupt police officer takes him to Sebastian, who wears a mask and administers the unwilling Mayor with a serum he calls "The Miracle". The precise effects of The Miracle are unknown, as are Sebastian's true intentions, but the serum caused The Mayor's eyes to bleed before possibly killing him. After injecting The Mayor, he instructs the officer to find him "another". The officer addresses him as "Brother Blood".
In "State v. Queen", it is revealed that he provided Count Vertigo with a means to redistribute his product, as he knew that it would flush out The Arrow so that Count Vertigo would kill him. Upon finding that The Arrow killed Count Vertigo rather than the other way round, he is initially angry, until he is informed that the first test subject has survived (or possibly awakened from) his exposure to the Miracle.
In "The Scientist", He was getting regular reports from Daily about movements begin conducted by three people looking into one of his test subjects, Maxwell Stanton's death. Blood gave Cyrus Gold locations of where to strike; Queen Consolidated's applied sciences division and a blood bank which were necessary for making more Miracle.
In "Three Ghosts",
- Brother Blood costume: Sebastian wears a costume as his villain alter-ego, Brother Blood, to hide his identity from his victims.
- Voice filter: Sebastian uses this device to change his voice regardless of who he spoke to as Brother Blood.
- In the comics, Brother Blood is the leader of the "Church of Blood", a cult that worships the demon warlord Trigon. He is a recurring enemy of Trigon's daughter Raven, and her friends, the teen hero group The Teen Titans.
- There have been multiple men who have carried the name "Brother Blood". However, Arrow's version of the character carries the name of the last Brother Blood prior to the New 52, named Sebastian.
- Sebastian is revealed to be allies with Slade Wilson who gives him blood samples to make Miracle.