[[File:AlastairKnife416.jpg|thumb|350px|Alastair survives being stabbed with [[Ruby's knife]].]]
Alastair has white eyes (including pupils and irises).<ref name="four09" /> His presence caused statues to weep blood<ref name="four09" /> and was noted as an expert interrogator and torturer,<ref name="four10" /> and was also incredibly resilient to being tortured himself; according to [[Castiel]], he had an exceptionally strong will, allowing him to withstand extended torture from both [[angels]] and one of his own apprentices.<ref name="four16" /> Alastair possessed an extensive knowledge of the occult as well as [[Enochian]] spells and rituals, including an incantation with an unknown negative effect on [[angel]]s,<ref name="four10" /> as well as another incantation that expels an angel from his [[vessel]] and sends him back to [[Heaven]],<ref name="four16" /> and spell-work to incapacitate [[reapers]].<ref name="four15" />
===Powers and abilities===
* Arcane knowledge – Being a [[white-eyed demon]] and presumably among the first created, Alastair possessed old and powerful knowledge, such as an [[exorcism]] ritual that could eject an angel from its [[vessel]] and send it back to [[Heaven]].
===[[4.16 On the Head of a Pin]]===
[[File:AlastairKilled.jpg|thumb|right|350px|Alastair is killed by [[Sam]].]]
Alastair has held captive by [[Castiel]] and [[Uriel]] and imprisoned in a [[devil's trap]] since the previous episode, but he refuses to tell them anything about the slain [[angel]]s. [[Dean]] is recruited as an interrogator because he was formerly Alastair's student during his time in [[Hell]]. Amused by the idea, Alastair taunts him over the course of the torture session, though he concedes that reality is "too concrete" compared to Hell for Dean to adequately torture him. Dean instead tortures Alastair with [[holy water]] injected into his veins, [[salt]] poured down his mouth, and mutilation from [[Ruby's knife]], as he admits to an unnerved Alastair he'd dreamed of doing in Hell. Instead of giving Dean the information he asks for regarding the angel murders, Alastair messes with Dean by claiming that he tortured Dean's father [[John]] in Hell and even made him the same offer he'd made Dean, but that unlike his son, John was a "hero" who steadfastly refused and ultimately escaped after 100 years (ten months on Earth) of Alastair's torture. Alastair gloats that when Dean accepted the offer in 30 years (30 months) and began torturing souls, he broke the first of [[the 66 Seals]] and enabled [[demons]] to begin breaking the rest of them. Having kept an eye on the devil's trap he's caught in being compromised - later revealed to be Uriel's doing, to let Alastair kill Dean and escape to make the angels keep thinking the demons are responsible for the angel murders Uriel committed - Alastair escapes when a devastated Dean turns his back, then begins savagely beating Dean again. He is about to finish Dean off and send him back to Hell, telling him he has a lot to learn, when he becomes distracted by Castiel intervening. Castiel embeds Ruby's knife in Alastair's shoulder and uses telekinesis to twist the blade, but Alastair simply pulls the knife out and fights Castiel. He again overpowers Castiel and while he is unable to kill the angel as he admits he wishes he could, he reveals that all he can do is send him back to [[Heaven]]. Alastair begins an angel [[exorcism]], but he is stopped by [[Sam]], who has become strong enough through his consumption of [[Ruby]]'s [[demon blood]] to overpower him with ease. Agonized by Sam's psychic torture, Alastair finally reveals that he knows none of the demons, including himself and [[Lilith]], are responsible for the angel deaths. Knowing that Sam can psychically [[exorcise]] demons, he challenges Sam to exorcise him back to Hell, where he wants to be, but is shocked when Sam instead uses his enhanced power to kill him.
===[[4.18 The Monster at the End of This Book]]===