Changes

Falling back under the Mark's influence, Cain descends into madness, believing that his bloodline is "tainted" and deciding to slaughter it despite it being "legion." He draws the attention of Sam and Dean and they team up with [[Castiel]] and Crowley to trap and kill him. After a brutal fight between them, Dean kills Cain with the First Blade when he refuses to give up killing once more.<ref name="ten14" />

===[[Dean Winchester]]===

After being killed by [[Metatron]], [[Dean]] is turned into a [[Knight of Hell]] like [[Cain]] as a result of the [[Mark of Cain]].<ref name="nine23" /> Due to becoming a demon through the Mark, and not centuries of torture in Hell, Dean was fundamentally different in that he still had vestiges of his humanity lingering within him. As a demon, Dean was free of his guilt, and engaged in all his vices to an excessive degree. He would eventually become too much for Crowley to handle, leading to Sam capturing him and administering the [[demon cure]] to an unwilling Dean.<ref name="ten03" />