The Circle of the Black Thorn was a secret society based in Los Angeles with ties to the law firm Wolfram & Hart. The Circle gathered some of the most powerful beings, economically, politically, and supernaturally.
History of the Circle
- “To be a Black Thorn is to be the Senior Partners' instrument on Earth. It doesn't get bigger than that.”
- ―Lindsey McDonald[src]
The origins of the Circle of the Black Thorn remained unrevealed, though it was likely that it was created after the Senior Partners, then known as the Wolf, the Ram, and the Hart, were driven away from this dimension. The members of the Circle, the self-fashioned Black Thorns, were considered the earthly instruments of the Senior Partners and were charged with the task of being the driving force behind Wolfram & Hart's apocalyptical plans and maintaining "man's inhumanity to man", not from a belief in evil per se, but because being a Black Thorn allowed them to amass power for themselves and wield said power with absolute impunity. However, for all their power, the Black Thorns still answered to the Partners for their actions. As an associated organization, Wolfram & Hart worked closely with the Circle and performed a number of services for its members.
As of 2003, the Circle's was composed by Archduke Sebassis, Senator Helen Brucker, Cyvus Vail, Ed, Grand Potentate of the Fell Brethren, the leader of the Sahrvin Clan, Izzerial the Devil, as well as three other men. Their latest recruit was Angel. Lindsey McDonald had hopes of joining the Circle by killing Angel, but these plans were foiled when he was defeated by Angel and Cordelia Chase. This and the fact that three of the members of the Circle seemed to be human, show that you don't have to be a demon to be a Black Thorn. Angel also stated that together the Circle was unstoppable and the most powerful group on this plane of existence, further showing their combined power. However, separately they were just demons and could be killed though given their individual powers, this was not easy.
Thanks to a vision given to him by Cordelia Chase before her death, Angel learned that the Circle represented the true powers behind Wolfram & Hart's apocalypse. However, the vision failed to show him their faces. After a lengthy investigation, Angel learned that he could only draw the attention of the Circle by sacrificing his role as Champion and killing one of his lieutenants. Taking advantage of subsequent events, Angel allowed the Circle to believe that he had orchestrated the death of Fred and her subsequent possession by Illyria.
In the following months, Angel pretended to become increasingly corrupted by his position as Wolfram & Hart's CEO. He helped the Fell Brethren acquire a baby to be used as a sacrifice on the child's thirteenth birthday , offered the firm's services in discrediting one of Senator Brucker's political rivals, Mike Conley, by brainwashing him to become a pedophile, and, finally, sent a demon assassin after Drogyn the Battlebrand, Keeper of the Deeper Well. After suitably impressing the Circle members, Angel was granted membership following an initiation ritual that included the torture of Drogyn, culminating in his death as he was drained by Angel. Angel thus accomplished his goal of discovering the faces of all the Circle's members, most of which he had already met during his time at W&H.
While pleased that Angel had joined them, the Circle remained wary that Angel would try to betray them as a way to fulfill the Shanshu Prophecy. They demanded that Angel renounce his claim to such destiny, a request to which Angel complied, taking advantage of the fact that the Circle wouldn't imagine that Angel would do good simply for its own sake rather than for a reward. However, the Circle would be unable to file the parchment before their demise the following night, leaving Angel's claim to the prophecy unchanged.
After Angel revealed his plot to his allies, he ordered them to spend the next day as though it would be their last- reasoning that it probably would be-, before they set out on their mission to destroy the Circle as an indirect attack on the Senior Partners; while the Partners themselves might be eternal and forever, Angel intended to show them that they would never control everything no matter how powerful they were and go out with a blaze of glory.
Izzerial and the three human Black Thorns were slaughtered by Illyria. The leaders of the Sahrvin Clan, including its Representative in the Circle, were slain by Lindsey with the aid of Lorne, who then turned on Lindsey and shot him at Angel's behest, Angel having noted that Lindsey would never be "part of the solution."
Gunn fought past the vampires staffing Senator Brucker's office and killed her with an axe to the head, although he himself was badly wounded in the process. Spike wiped out the Fell Brethren and Ed, their Grand Potentate, while rescuing the infant they had desired to sacrifice.
Wesley Wyndam-Pryce faced Cyvus Vail, though he was unable to defeat the powerful warlock, merely throwing him around with a couple of well-placed fireballs. Vail lethally injured Wesley, only to be slain by Illyria after Wesley died in her arms.
Angel secretly poisoned the Archduke Sebassis via the slave demon the duke drank blood from, and subsequently killed Marcus Hamilton, the Liaison to the Senior Partners, with the aid of his son Connor. After a long fight, despite Hamilton's superior strength, Angel learned that Hamilton's blood was the source of his power, and managed to acquire some of it by drinking his blood. Empowered by Hamilton's blood, Angel succeeded in killing the Child of the Senior Partners. 
After the battle, Angel, Spike, Illyria, and Gunn gathered in the alleyway behind the Hyperion Hotel to face the army that had been sent to kill them for their actions, only to be taken aback when the Senior Partners punished them by sending the entire city to Hell. Despite the odds against them (including Gunn being sired while Angel was turned into a human), the team were eventually able to return the city to Earth thanks to Angel provoking Gunn into killing him, the Partners' plans for Angel forcing them to turn time back to the last moment when he was in one piece (the fight in the alleyway) apparently expending significant resources in the process.
Five years later, according to the Slayer Buffy Summers, the Archduchess Venobia, from the same specie to Sebassis is a member of the Circle. It was unknown if her allegeance existed during Angel Investigation's era or if there is a new circle apparently in allegeance with the Vengeance demon D'Hoffryn.
- Archduke Sebassis (Leader; deceased)
- Cyvus Vail (deceased)
- Izzerial the Devil (deceased)
- Senator Helen Brucker (deceased)
- Grand Potentate Ed of the Fell Brethren (deceased)
- The Leader of the Sahrvin Clan (deceased)
- Three unidentified humans (deceased)
- Angel (infiltrator)
- Archduchess Venobia