I'm not sure why this idea popped into my head all of a sudden after watching the third trailer for Chris Nolan's The Dark Knight Rises, which btw I thought was epic and didn't show too much, no ne still knows what's going to happen. I think Bane's going to go down as one of the all-time greats in terms of movie villains, not just CBMs, right up there with The Joker, Javier Bardem's Anton Chigurh from No Country for Old Men, and all of the other greats.
But Anyways, I came up with a possible explanation and backstory for Bane- It's almost confirmed that he is a member of the League of Shadows, and maybe he was with Ra's al Ghul when he tried to destroy Gotham in Batman Begins. He didn't have the mask yet, and was one of his soldiers, possibly one of the ones dressed in a ninja-like outfit who Batman fought as Ra's got away. He sees the train crash, and goes to see if Ra's is still alive, Ra's is just about dead, but tells Bane who Batman is and makes him promise to accomplish the feat that Ra's couldn't- destroy Batman and his city. Bane tries to carry Ra's through the FIRE, hence the "Fire Rises" thing and Bane's injury that makes the mask vital for him to stay alive. Bane goes into hiding for awhile, watching all of Batman's moves, including his battle with the Joker, and begins to plan his attack, thus the events of The Dark Knight Rises.
So what do you guys think? I know it's a long shot, but I just thought it was a cool theory that could help with the "bringing the trilogy full-circle" thing. Share your theories below!