Alastair is a uber-powerful demon first introduced to the viewing audience as a demon in search of Anna, the fallen angel that at the time seemed to just be a regular girl with the ability to hear Angelic conversations. The Winchester brothers have located Anna but are quickly interrupted by Alastair's arrival. Sam and Dean are forced to fight Alastair who proves to be far too powerful for the brothers. During the scuffle it is revealed that Alastair is the Demon who was in charge of torturing Dean during his 40 year stint in Hell.The Winchesters of course survive this encounter but they once again meet up with alastair in a barn where the demons and angels clash for the first time in the series. Alastair is defeated and captured, and the angels ask Dean to use his torture abilities (the ones he learned in hell) to get information out of alastair. Dean agrees but during the torture, alastair gets free. But before Dean is killed, Sam arrives in time to excorsize Alastair back to Hell with his mind.