Just one example of the new mechanics you can expect from the expansion is the new vehicle-based content, which puts an interesting spin on some of the concepts originally developed for PvP siege gameplay. Certain types of vehicles and mounts can now carry passengers, making it possible for players to, for example, break a prisoner out of a tightly guarded compound by attempting a daring escape on horseback. While the NPC steers the horse, the player lobs explosives at a pack of pursuing worgen. In another quest, the roles are reversed as the player takes to the skies in a flying machine to track down and rescue survivors of a catastrophic event. Even beyond the ability for vehicles to hold passengers, Wrath of the Lich King introduces an aerial combat system that will add a new dimension to gameplay.