What are Heroic difficulty dungeons?
Introduced in The Burning Crusade, Heroic-level instances are alternate versions of the new five-person instances that have been considerably increased in difficulty, and have their own set of more powerful rewards. Access to Heroic difficulty requires each group member to have Honored reputation level with the dungeon’s associated faction in order to purchase the appropriate key. Once everyone in a five-person group has the key to unlock Heroic difficulty for an instance, the group leader simply has to set that instance to Heroic in the group leader menu.
