History of Blood
The first Brother Blood was the high priest of the Baltic country of Zandia who refused to supply recruits for Pope Innocent's Fourth Crusade in 1202. During the ensuing battle, the high priest gained the Cloak of Christ, allegedly worn at the Last Supper, but now corrupted with evil. Wearing the cloak, the priest led his knights to victory. He then bathed in his enemies' blood, which gave him great strength and virtual immortality. The priest declared himself Brother Blood and closed Zandia to all strangers, except those who will join his church and plege all they have to the church.
He ruled for 60 years, fathering a son who killed him at age 100. So began the terrible Curse of Blood, whereby each son of Zandia's ruler slew his father, bathed in the Bloodpit, then ruled in his place.
Chronologically Brother Blood is first encountered by the New Teen Titans, as the leader of the Chruch of Blood and Zandia, when he attempts to spread his faith to the US. The Titans become suspicious of him and his church when a former girlfriend of Cyborg attempts to flee the church only to be shot while calling him for aid. The Titans later learn that Blood was using the church to convert people to his cause and ultimately attempt to sieze control of the world. While Blood's initial attempt was halted with him seemingly killed in the process, it turned into a pr-disaster for the Teen Titans, as one of Blood's devotees was a highly regarded journalist, who painted the Titans as terrorizing a peaceful congregation for no reason. Blood however had engineered the whole thing and went underground to prepare for the next part of his plan.
Having realized the power that lay within Raven and how he could use it, Brother Blood pursued the Titan that had been lost since the Terror of Trigon, eventually settling on following Arella who was also in pursuit eventually capturing both. Because of Raven's fragile state of mind following the battle with Trigon, Blood had little difficulty turning her to his side, causing her to constantly make everyone around her feel better. When Nightwing was later captured as well, Blood had Raven heal Nightwing after each session of torture.
When the time was right, Blood instigated his own televised rebirth, and Titan support through Raven and Nightwing, while his own empathic powers swelled as millions started to believe in him. Again he was confronted by the Titans but defeated them easily. But due to the jealousy of Mother Mayhem towards Raven, his second in command and mother of his child, and his own greed and arrogance, he pushed Raven to a point where her mind snapped back into place and she turned on him in rage, rendering him into a meek shepherd.
Some years later, a new Brother Blood would emerge to battle the Outsiders. Being described as an arms-dealer, the second Brother Blood was later found murdered in the ocean.
This gruesome pattern of events has recently continued as yet another son has killed his father. However, this particular 14-year-old lacks the training of his predecessors. Instead, his ultimate goal is world domination using his church's might. The Outsiders and Teen Titans, though, stand in his way. He tried to wed Raven, as a part of a prophecy to bring Trigon to Earth. He was stopped. He later tried to take over the world again, starting with the Teen Titans, by stealing Kid Eternity's powers. He raised the dead Titans, planning to kill the living ones. He was stopped by Kid Eternity, who brought back the former Brother Blood's, who tore Sebastian to shreds.
He grew up in Hell, having been tortured for so many years even he can't recall how long. He believes that being there is all part of Trigon's plan. Then one day the magical binds holding him, break, setting him free, turns out all the prisoners in hell have been set free. He sets out to find Trigon, to be his loyal soldier, but is attacked by a demon with tiny mouths on his fingers, who starts drinking his blood. Brother Blood then gains the upper hand and bites back, finds out the demon has a healing factor, and rips his arms off. He then finds Kid Eternity and tells him to look at his killer. Kid Eternity turns into Aquagirl getting a few punches in before his power runs out. Brother Blood comments on Eternity's power loss, then bites him, teleporting them to Titans Tower. Brother Blood then bites Misfit, uses her powers to teleport, then bites Wonder Girl's leg, leeching her powers. Brother blood then bites Red Devil, but says his blood is tainted by Neron. He then uses Red Devil's power to make a portal. He then starts searching for someone to be his 'mother'.
First appearing in an ominous dream of Beast Boy post Flashpoint, the helmet he is seen wearing suggests that he is Sebastian Blood. He next appears emerging from a pool of blood, talking to three women who tell him how to open a portal to the Red using the blood of the Ravagers and that one of them is the key. Unlike the previous presentation of Sebastian, he appears rather irreverent and refers to his fleshless acolytes as 'morons' as he dispatches them to capture the targets. When they resist his acolytes, he shows up and heals Lightning, taking control of her as he touches her blood. He proceeds to drain blood from Thunder as the others are captured. Back at the sanctuary of the Church of Blood, he recognizes Beast Boy from a dream. He tries to charm Terra before battling the crimson changeling. Lighting's leap into the portal causes it to blow up and bury him under rubble though he still seems to be alive.
Brother Blood would later attempt to gain access to the Red Kingdom, gaining the favor of one of the Totems before murdering most of the others before being confronted by Animal Man.
Powers and Abilities
The first Brother Blood encountered by the Teen Titans was a powerful orator and in possesion of several superhuman powers, such as superstength, durability and some empathic/psionic abilities that he uses to sway people to his cause while mostly rendering him immune to Raven's powers. He was skilled planner and had tremenous resources backing him as the ruler of Zandia and a following who donated everything to his church upon entry.
Sebastian Blood is able to steal powers vampirically, being strong enough in the first encounter overpower and bite through Superboy's skin. He has some influence over Raven if her chakra (The emblem on her forehead) stone is removed from her forehead, but it waves with distance. He leads a cult of devoted followers originally in the service of Trigon.
The followers in the N52 appear to be people with their skin ripped off. He refers to them as "Morons". He is able to heal wounds just by touching the persons blood, like with Lightning. He has also shown the ability to actually drain people of their blood instead of sucking it like most vampires. He also seems to naturally possess super strength and durability. He has also shown the ability to manipulate blood to great detail, and shoot lightning out his hands. He no longer has shown to possess his ability to take powers for short periods of time in the New 52, but his base durability and strength are enough to fight Animal Man and Beast Boy (at different times). He has shown the ability to paralyze Superhumans (The Ravagers in specific). It is unknown how he done this.
Brother Blood appears in the Teen Titans TV show as the headmaster of the H.I.V.E. Academy, having been based on the original Brother Blood. His prised students count Jinx, Mammoth and Gizmo. He is shown to have a strong interest in Cyborgs robotic body as he was the only person Blood knew who could resist his hypnotic powers and later in the show he willingly becomes half robot, but still retains all the speed and skill he possesed before, remaining a formiddable combatant.
Sebastian Blood first appears in Season 2, Episode 2 of Arrow: "Identity." Kevin Alejandro plays Blood, an Alderman claiming to be a helpful force for The Glades. Sebastian Blood turned to be "Brother Blood", "The man in the skull mask" and turns out to be working for Slade "Deathstroke" Wilson. Sebastian later dies at the hands of "Ravager" during Season 2 Episode 22 of Arrow "Streets of Fire" after betraying Deathstroke by giving Oliver Queen the cure.