The Church of Blood is a secret following formerly led by Slade Wilson. Sebastian Blood served as a front for the Church, until he betrayed the organization. Due to his betrayal, he was killed by Isabel Rochev on Slade's orders. After Slade was imprisoned by A.R.G.U.S. and Isabel was killed, leadership of the Church was taken over by Clinton Hogue, who took up the mantle of Brother Blood.
Sometime after The Undertaking, Sebastian Blood, under the instruction of Slade Wilson, formed the Church in Starling City, and claimed to be the leader of The Glades as its alderman. He then recruited people into his cause and decided to use an army "of the strong", basically consisting of those who survived his test.
On the outside, Sebastian Blood as an alderman, he was a well-liked, charismatic person who knew how to win a crowd within the Glades, and had the support of those who had been devastated by the Undertaking.
Sebastian's plans were unknown, but he stated that he wanted control of Starling City, and had an apparent vendetta against The Arrow, as he was disappointed by the news that Count Vertigo was unable to kill him after being resupplied with his operations in Starling City, by Brother Blood.
The background of the Church of Blood is currently unknown, though sometime after the Undertaking, Sebastian supplied Count Vertigo with what he needed to restart his Vertigo operations, but by the time Oliver Queen returned to Starling City after being on Lian Yu following the events of the Undertaking, Sebastian has become a well liked person and the people of the Glades seeing him as a leader with signs saying "Blood for Mayor" during the events of "City of Heroes". At some point, he hired the Hoods to assassinate the mayor of Starling and clear the way for his own mayoral candidacy.
Sebastian has gone to even criticizing Oliver Queen in the media after he was unable to attend an event he put together to make amends with Sebastian who didn't have a very good opinion of him and the Queen Family during the events of "Identity".
He then met with The Mayor in "Crucible", after he was arrested by the Starling City Police Department after a fight with The Arrow and The Canary where he is injected with The Miracle, possibly killing him.
In "State v. Queen", Sebastian sent Count Vertigo to kill The Arrow only to fail and be killed himself, one of his agents reported that there was progress, after dressing up in his costume, Sebastian and Daily approach one of the surviving members Cyrus Gold asking how he felt, when he said he felt stronger, Sebastian told him he was ready to begin.
During "The Scientist", Cyrus Gold now infused with Miracle begins immediate assaults on Queen Consolidated's applied sciences division and a blood bank for equipment to mass-produce the Miracle. On the third stop which was an A.R.G.U.S. bunker, he attacks Oliver Queen using his strength which causes Oliver to slam into a shelf and is drugged and left for dead.
Sebastian injects Roy with the Miracle as Oliver arrives to save him but is announced dead, after getting a second wind, Oliver attacks and kills Cyrus with an arrow to the centrifuge that was producing the Miracle. Roy later is brought back to life by Oliver after performing CPR.
Later on, Sebastian announces his decision to run for Mayor of Starling City on television while he goes to meet his boss who tells him that he will provide him with another sample of his blood to produce more Mirakuru. His boss is revealed to be none other than Slade Wilson, who had been presumed dead. Slade informs Sebastian that he is not to engage The Arrow directly or Slade will find another to wear his mask. When questioned, Slade tells Sebastian that he will take away everyone and everything he cares about and when that is done, he will personally drive an arrow into Oliver's eye.
Sometime later in "Blind Spot", Sebastian murdered his mother Maya Resik after she told Laurel Lance the truth about Sebastian, that he murdered his father and placed her in a mental ward. Afterwards, Slade ordered Blood to handle Laurel, which resulted in Daily arresting her for possession of controlled substances.
Upon her release, she is captured by Sebastian and sent to an unknown location where she was going to be killed by a man wearing Blood's mask. The Arrow and Laurel defeat the masked man, who is revealed to be Officer Daily. Blood then returns to Slade who tells Blood that he failed once again, killing Blood's two bodyguards and pointing the tip of his sword at Sebastian's throat, warning him that if he failed one more time, then he would be the next to die.
In "Heir to the Demon", Slade watches the news report of Moira Queen's announcement of her entry into the race for mayor; he reminds Sebastian not to underestimate her. Sebastian meets with her and threatens her to withdraw from the race and give up on winning, wondering which Moira Queen would be the face of the campaign: the Moira who was the victim of Malcolm Merlyn, or the one who could lead the city away from fear.
Slade tells Sebastian that he will handle Moira when he questions what they will be doing moving forward.
In "Deathstroke", Isabel Rochev uses Thea's kidnapping to trick a distracted Oliver into handing control of Queen Consolidated over to her, and has the board of the company oust Oliver and appoint her as permanent CEO. She briefly battles Oliver, revealing that she has been working with Slade Wilson all along and that she only bought Queen Consolidated's stock to lure Oliver back to Starling from Lian Yu.
Meanwhile, Deathstroke hijacks a prison bus headed for Iron Heights Prison. He kills the guards and frees the prisoners, recruiting them into the Church of Blood. Later, he meets with Sebastian Blood and Isabel at Queen Consolidated, where Isabel confirms that Queen Consolidated's applied sciences division is now dedicated to mass-producing Mirakuru, which they will use to create an army of super-strong soldiers to conquer Starling City.
In "The Man Under the Hood", Deathstroke looks for an alternative way to infuse his army of prisoners with Mirakuru after Team Arrow blows up Queen Consolidated's applied sciences division. He captures Roy, infiltrates the Arrowcave, attacks Team Arrow, and steals the Clock King's skeleton key. With the key, he breaks into S.T.A.R. Labs and steals a bio-transfuser which he uses to transfuse the Mirakuru from Roy's blood into his army. Eventually, the Arrow tracks down the bio-transfuser with Felicity's help, and confronts Slade and Isabel. He shuts the machine down and escapes with Roy. During the battle, Isabel is shot through the chest by Diggle. Later, Slade is seen having used his own blood to complete the Mirakuru transfusion into the prisoners and Isabel, who is revived.
In "Seeing Red", Slade causes a limo carrying Oliver, Moira, and Thea to crash. He then captures all three of them and then re-enacts the occasion of Shado's death, this time forcing Oliver to choose whether to kill Moira or Thea instead of Shado or Sara. Eventually, Moira offers to sacrifice herself to spare Oliver and Thea. Slade commends her courage, then kills her with his katana.
In "City of Blood", Sebastian is sworn in as mayor, having won the election by default after Moira's death. Isabel visits the reception to Moira's funeral to taunt Diggle and Felicity, telling them that they will be the next to die. Isabel manages to have Verdant taken from Thea. Laurel plants a bug in Sebastian's office which allows the police to hack his computer, and discovers a press release offering his condolences to the Queen family, dated the day before Moira's death - incontrovertible proof that Sebastian knew that Slade was going to kill one of the Queen family which Laurel tells Oliver about, making Oliver realize that he had been deceived all this time.
Armed with this information, Oliver confronts Sebastian and reveals that he knows Sebastian is working with Slade Wilson, as well as his secret identity as the Arrow. Sebastian claims that after Slade's army is done with Starling, the people will flock to him for leadership, and he can rebuild the city according to his vision but Oliver tries to convince him that Slade will not deliver on his promise and that he is a pawn though Sebastian refuses to listen.
Later Brother Blood rallies Slade's army of Mirakuru-enhanced soldiers, preparing to lead them in their assault on Starling City. One soldier is sent to the police station, where he kills Kelton and battles Quentin Lance, while another is sent to attack the train station where Thea happens to be. Team Arrow attempts to destroy Slade's army's hideout with explosives and bury the Mirakuru-enhanced prisoners and Blood inside, but before Diggle can trigger the explosion, he is attacked by Isabel, as Ravager.
In "Streets of Fire", Slade's army continues tearing apart the city. Felicity rescues Diggle by running Ravager over with a van and driving away with him; Ravager survives thanks to the Mirakuru. Slade overhears Oliver talking to a S.T.A.R. Labs courier who is carrying the Mirakuru cure, and sends his soldiers to retrieve it. As Oliver, Diggle and Felicity drive to the courier they are attacked by Mirakuru soldiers who topple the car and Felicity is knocked unconscious, but Oliver uses an explosive arrow to knocked out the attackers. However the Mirakuru soldiers arrive to the courier, kill him and steal the cure before Team Arrow can get there. Laurel Lance is almost cornered by a soldier but Sara Lance/The Canary. Meanwhile, Quentin Lance stops the Mirakuru soldier in the police station by blowing him up with grenades, and Malcolm Merlyn/Dark Archer kills a Mirakuru soldier at the train station to save Thea. Malcolm then faces another Mirakuru soldier, or possibly the same one, trying to kill Thea and manages to kill him.
At the mayor's office, Sebastian Blood is commanding the city's response to Slade's attack, convincing D.A. Spencer that he has things under control. However, one of Slade's soldiers bursts into the mayor's office and kills Spencer, despite Sebastian ordering him to stop. A furious Sebastian confronts Slade, saying that he wanted only to cause enough damage so that he could rebuild Starling City according to his vision, not destroy it completely. Slade is coldly indifferent and insists that the only thing that matters to him is hurting Oliver Queen, and that the total destruction of Starling is part of that aim.
Sebastian responds by stealing the Mirakuru cure and delivering it to Team Arrow. He justifies his actions to Oliver by saying that he has always wanted what's best for Starling City and vowing to redeem himself by rebuilding it after Slade is stopped. An incredulous Oliver asks him if he really thinks the city will let him continue as mayor after what he's done; Sebastian replies that no one but Team Arrow knows of his involvement and threatens to reveal the Arrow's secret identity should Oliver ever tell the world of Sebastian's actions as Brother Blood. Isabel then arrives at the mayor's office, asking Sebastian where the cure is. When he tells her he has already given it to Oliver, she stabs him to death on Slade's orders. Slade's army attack causes Amanda Waller to send A.R.G.U.S. troops to secure the city exits and prepare an airstrike from a predator drone.
In "Unthinkable", as the attack continues the Mirakuru soldiers attack the church tower where Team Arrow is, after successfully testing the cure on Roy, and escape by sliding down a cable as Lyla Michaels arrives to blow up the tower. The Arrow and the Canary using cure arrows invade Queen Consolidated where Deathstroke, Ravager and a dozen Mirakuru soldiers are waiting. However they are surprised by the arrival of the League of Assassins lead by Nyssa al Ghul, who kills Isabel, while everyone else is cured though Deathstroke manages to escape. On the news Bethany Snow reports Sebastian's death.
The Mirakuru soldiers aware of the impending airstrike were ordered to escape through the tunnels while one injured Quentin and kidnapped Laurel from the S.C.P.D. Arrow, Canary, Roy, Nyssa and the League attacked the army in the tunnels and cured most of them. As one was about to kill Sara, Nyssa cured him but as another almost killed Nyssa but Quentin arrived in time to cure him and reluctantly saved Nyssa. Meanwhile, Deathstroke kidnapped Felicity believing her to be Oliver's true love, as part of a deception between the two.
Slade forced the Arrow to arrive alone where he and a soldier had Felicity and Laurel but Felicity cured Slade while the Canary cured the soldier and got Felicity and Laurel away as Deathstroke fought the Arrow. Eventually after a prolonged fight Oliver was able to restrain Slade to a pillar and ordered Waller to stop the airstrike, before incarcerating Slade in an A.R.G.U.S. super-max on Lian Yu itself.
- Roy Harper (unwilling test subject)
- Slade Wilson/Deathstroke (leader and benefactor for the Mirakuru; incarcerated)
- Mirakuru army (soldiers; most incarcerated)
- Abel (second-in-command; possibly)
- Sebastian Blood/Brother Blood (official leader; third-in-command)
- Daily/Brother Daily (spy within Starling City Police Department)
- Cyrus Gold/The Acolyte
- Caleb Green
- Clinton Hogue/Brother Blood (leader)
- Xavier Reed/The Mayor (unwilling test subject)
- Isabel Rochev/Ravager (spy within Queen Consolidated; second-in-command)
- Max Stanton (unwilling test subject; deceased)
- The Technician (scientist)
- Mirakuru army (soldiers; some deceased)
- John Diggle
- Nyssa al Ghul
- Roy Harper/Arsenal
- Laurel Lance
- Quentin Lance
- Sara Lance/The Canary
- League of Assassins
- Malcolm Merlyn/Dark Archer
- Moira Queen (deceased)
- Oliver Queen/The Arrow
- Thea Queen
- Felicity Smoak
- Amanda Waller (deceased)
- In the DC multiverse, the Blood Cult, rather than the Church of Blood, worships the demon Trigon, the father of Teen Titan Raven.