Larger in size than the Eastern Plaguelands, Hellfire Peninsula is the home of three key points of interest: Thrallmar the Horde quest hub (completing quests yields increased reputation with Orgrimar); Honor Hold the Alliance quest hub (yielding rep with Stormwind); and Hellfire Citadel the giant, instanced "level-up dungeon." Thrallmar and Honor Hold both serve as their factions expeditionary bases, but Hellfire Citadel is controlled by the Fell Orcs, the remnants of the Orcs that didn't make it through the Dark Portal who have succumbed to the curse of the demon blood that sustains them.
It is within Hellfire Citadel that the Fell Orcs have trapped Magtheredon, a pit lord, and tap his tainted blood to feed their unending thirst. While Magtheredon is essentially a raid-boss for those who get to the new level cap of 70, Hellfire Citadel has numerous wings to explore, each tailored to a specific level range, so that any 60+ level character will feel right at home (or as "at home" as you can feel surrounded by bloodthirsty Fell Orcs).
In addition, Outland will contain numerous outdoor "points of interest," outdoor PvP hubs that grant specific bonuses to the faction that holds them. Bonuses such as granting extra experience, increased damage or access to new flight paths serve as incentives for capturing individual PvP hubs in the zone. These outdoor PvP hubs won't be limited to just the Outland, however, and Blizzard plans to implement them across Azeroth as well when they issue the Patch 1.12 content update.
