Can I use Bran's interrupt ability, but use a duplicate to save him from being sacrificed? No, see page 18 of the RRG. If the chosen card does not leave play, the sacrifice is not considered to have been made. A sacrificed card cannot be saved.
House Stark. Non-Loyal.
Character. Cost: 2. STR: 1.
Interrupt: When the effects of an opponent's event would initiate, sacrifice Bran Stark to cancel those effects.
"Can a man still be brave if he's afraid?"
Core Set #142.