Crowley

Crowley is Lilith's right hand man and possible lover. At the end of Season 3 Bela told Dean that she had given the Colt gun to Lilith when it is reveled in "The Real Ghostbusters" that in fact she gave it to Crowley, this was discovered after super fan Becky told Sam she read it in Chuck's stories. Castiel tracked Crowley to his Enochian protected mansion after witnessing him make a deal with a 60 year-old businessman.

Sam and Dean killed Crowley's demon gate guards and broke into the building, cutting off the power. Crowley approached them openly, however, and used the Colt to kill his other guards. Crowley gave the Colt to the Winchesters and asked them to kill Lucifer as he believed the fallen archangel held no love for his human-spawned creations and would quickly seek their destruction once the humans were all wiped out.

Sam tried to shoot Crowley, but the weapon wasn't loaded, so Crowley provided him with some ammunition before promptly vanishing on the spot.

Trivia

• It is implied that Crowley is a Crossroads Demon, as he is seen making a deal with a man after being summoned in the same manner as other Crossroads Demons (also requiring a kiss to seal the deal).