Alastair is a [[Demon|white-eyed demon]]<ref>[[4.09 I Know What You Did Last Summer]]</ref> responsible for torturing human souls in [[Hell]]. He is held in high esteem by many of his demon comrades, he is referred to by [[Ruby]] as "practically the Grand Inquisitor downstairs." He possesses an extensive knowledge and awareness of the universe, having occult knowledge, usage of spells cast in [[Enochian]] as well as rituals.
Alastair was initially immune to [[Sam]]'s psychic abilities,<ref>[[4.09 I Know What You Did Last Summer]]</ref> although, ironically, he is eventually killed by them.<ref name="four16">[[4.16 On the Head of a Pin]]</ref> His durability seems to exceed that of most demons' as [[Ruby's knife]], a weapon that can kill demons, only greatly
damage him but did not kill him.<ref>[[4.09 I Know What You Did Last Summer]]</ref><ref name="four16" />
As a torturer, he is an expert interrogator in that regard
, according to [[Castiel]], he had an exceptionally strong will, allowing him to sustain himself while being tortured.<ref name="four16" /> [[Meg]] was an apprentice of him before his death.<ref name="six10">[[6.10 Caged Heat]]</ref> He tortured both [[Dean]] and [[John Winchester]], and in both instances offered to end the torment if they would become torturers themselves. Alastair reveals that the first seal was broken when Dean accepted this offer.
can send an [[angel]] back to [[Heaven]] by expelling it from its [[vessel]].<ref>[[4.10 Heaven and Hell]]</ref><ref name="four16" /> Alastair has shown to be resistant to an angel's power of [[exorcism]].<ref>[[4.10 Heaven and Hell]]</ref> He possess knowledge of the [[Four Horsemen of the Apocalypse]] and has demonstrated power to overwhelm a [[reaper]].<ref>[[4.15 Death Takes a Holiday]]</ref>