Supernatural: Why Did Crowley Team Up With Sam & Dean In Season 5?
Considering the fact that brothers Sam and Dean Winchester (Jared Padalecki and Jensen Ackles) spent Seasons 3 and 4 of "Supernatural" trying to defeat the white-eyed demon Lilith (Katherine Boecher), it was certainly quite a shock when the brothers decided to partner up with her chief advisor in Season 5.
That season saw the Winchesters forming a reluctant alliance with Lilith's former ally Crowley (Mark A. Sheppard), a relatively weaker demon with a talent for manipulation and an incredible level of ambition. After Sam killed Lilith and allowed Lucifer (Mark Pellegrino) to escape hell, Crowley abandoned demonkind and started plotting against Lucifer — believing that Lucifer would massacre all demons after he had eradicated humankind.
This shared goal of defeating Lucifer is the only reason that Crowley and the demon-hunting brothers began working together. After initially providing the Winchesters with a demon-slaying revolver known as "The Colt" (which fails to kill Lucifer, since he is too powerful) Crowley assists the brothers in tracking down the Four Horsemen of the Apocalypse and claiming their "Rings." In the Season 5 finale, Crowley and the Winchesters use those rings to re-seal Lucifer in Hell, which allows Crowley to ascend the throne as the new King of Hell.
Crowley switches sides constantly throughout Supernatural
While the malicious Crowley did help to take down Lucifer in Season 5, his relationship to Sam and Dean Winchester was incredibly rocky over the course of the entire series.
In Season 6, Crowley fools the Winchesters into helping him search for Purgatory. He promises to help Sam reclaim his lost soul, while secretly planning to use the lost souls of Purgatory to gain an immense level of power. Despite this betrayal, the brothers would partner up with Crowley again in Season 7 to take down the Leviathans. Season 8 even saw Crowley turn into a full-blown antagonist, working to bring a horde of demons down to Earth, killing people that Sam and Dean had helped in the past, and eventually being imprisoned by the brothers in the season finale.
Throughout the series, it's made clear that Crowley's charm is a mask for his sadistic, vengeful nature, and for much of "Supernatural," he is presented as a selfish character who only looks out for himself. In the end, however, Crowley embraces his antihero nature and the small bit of humanity that he has gained from working with the Winchesters, sacrificing himself to trap Lucifer in another dimension and saving the world in the Season 12 finale.