Heroes & Maps Pack includes two new multiplayer maps, two Hero Arenas and three new heroes.
Holds on to the No.1 spot for the first time since it launched nine months ago.
Celebrates its fifth week at the top thanks to a 18% rise in sales.
Director Eric "Giz" Gewirtz on hobbits, Balorgs and burning the Shire to a crisp.
Pandemic's action game set is coming to Xbox 360, PS3, PC and Nintendo DS.