HE TOTALLY WOULD JOIN. THEY'RE NOT PEOPLE AFTER ALL.

Blathazar is totally curious as to who the the man who changed his once-uptight friend is. He's tried for centuries to get Castiel to loosen-up some, be less dogmatic, and this lesser being arrives and accomplishes it in less than a year. Not only that he gets Castiel to rebel and almost fall and become a revolutionary in heaven. He's curious, yes, but he's totally jealous.

YES. OMG, DEAN! IS DEAN GOING TO FAIL DEATH'S DEAL?