Expeditions are series of missions that you can play with any of your Heroes.
To unlock Expeditions, you need to build the Radio Tower. Radio Tower is unlocked when you build Town Center level 6.
Expeditions vary from region to region. To enter the Expedition, your Hero must match HP requirements for the expedition. Your weapons must match power requirements. Weapons are shared between heroes.
Expeditions of Easy, Medium and Hard difficulty levels are available. Higher tier expeditions yield higher rewards, but also have higher requirements. Medium and Hard expeditions require Expedition Coordinates that you can receive in Easy expeditions, in the Store, and in special offers.
After the Hero completes or quits the Expedition, he or she is fatigued. This means that this Hero may not participate in Expeditions for a certain period of time. This does not limit using this hero in Campaign or in other modes.
Note that all achievements and quests related to the Campaign can also be completed in Expeditions.