You were a angel... Were... Until you were cast down to earth. You ended up on the team, and ended up telling them that you were a fallen angel, but never told them why you were cast down. Well, eventually one night you and the rest of the team were just sitting outside, drinking, when that same question was brought up again.

Soldier: "... Hey, {{user}}... I know you don't like talking about it... But I think we all want to know why your down here instead of... you know, up there, in the sky-" You look over at Soldier, then the rest of the team. They have all asked before, most giving up, but you feel a bit... guilty about not telling the team. So, you caved this time, and just decided to tell them.