Christopher Nolan is old school. He doesn't save his surprising reveals for the credits, he keeps 'em in the damn movie.
I still remember the yawps of nerdish glee upon seeing the Joker card at the end of "Batman Begins," and "The Dark Knight Rises" has its share of ZOMGs during its final act as well.
I'm not about to take that experience away from you with the new one, but some of the impact may be lessened if you only have a hazy memory of Nolan's first film and the mysterious "League of Shadows." Allow me to hum a few bars to remind you.
If you recall, young Bruce Wayne goes on an epic walkabout in "Batman Begins" and finds himself in the Himalayas. He finds himself under the tutelage of Liam Neeson's Henri Ducard, a recruiter and advance man for the League of Shadows.
Here he learns advanced ninja skills as well as the importance of PSYOPS and showmanship when hoping to beat the hell out of your enemies. He's also taught how to embrace and exploit fear, seeding the idea to delve into his childhood traumas. (He also goes on a quest for a blue weed in the snow, which photographs really well.)
He soon discovers that the League's call for social justice is a little more extreme that merely boppin' someone on the head and calling the chief of police to come pick 'em up. It's here, when Wayne is asked to commit a summary execution, where one can argue that Batman really "begins."
Later in the film we learn that Ducard is not who he says he is. He is actually the League's spiritual leader R'as al Ghul. (Yeah, that name's a lot more scary, right?)
Like Aslan and Qui Gon-Jin, Neeson's character is someone who may have lived through the ages (hardcore comics nerds know all about the Leagues' access to "Lazarus Pits") and his methods may have been responsible for the sacking of Rome, the Black Plague and, if Batman doesn't stop them, the destruction of Gotham City.
The League isn't too involved in "The Dark Knight," but in "The Dark Knight Rises," when Bane is introduced as someone who was excommunicated from the League, you can rest assured that this is a guy who plays for keeps and has nefarious plans as well as humongous muscles up his sleeve.