|Episode(s)||14.07 Unhuman Nature|
Sergei is a shaman who used to consult for the British Men of Letters when they would come across an unsolvable problem. Sergei prefers not to have roots, claiming to have crossed the globe many times over to study and observe the skills of myriad witches, seers, and holy men. As a shaman, Sergei tries to "answer the unanswerable" and "know the unknowable" but considers himself first and foremost a healer.
After speaking with Ketch about Jack's situation, Sam is directed to Sergei, a shaman that the British Men of Letters have sworn by to help "solve the unsolvable" in the past. While Dean takes Jack out for a bit, Castiel decides to take the meeting Ketch has set up, and drives out to meet with Sergei.
Arriving in a wooded area, Castiel begins walking to a trailer only to be stopped by a ring of holy fire. Sergei steps outside, shotgun in hand, and asks if Castiel brought anyone else with him. Once he is sure Castiel is alone, he invites him inside for some tea. Sergei give Castiel his "curriculum vitae", explaining his qualifications before moving onto the subject of Jack. He tells Castiel he does not believe Jack's condition can be reversed, but his system can be shocked to stop the progression. When Castiel asks how they could possibly achieve that, Sergei produces a vial of archangel grace which he says is from Gabriel, explaining that he bartered a cloaking spell which allowed Gabriel to hide away in Monte Carlo for it. Handing it over to Castiel, he tells him they will need to recite a specific spell, then hands him the box which contains it. Castiel questions what the cost would be, but Sergei tells him his services are for barter only, and to tell the Winchesters that they "owe [him]."
After administering the grace to Jack to no avail, Castiel places a call to Sergei demanding his help, as Jack's condition has worsened. A disinterested Sergei explains that science is "trial and error." As Castiel threatens to find him if Jack dies, Sergei simply chuckles and dares him to try.