Mission is an unlockable daily activity available at Headquarters, and essentially another type of combat you can engage in on a daily basis for additional Income. It can be unlocked at a cost of 5 and be initiated indefinitely afterwards. Every day your armies are randomly assigned to 1 out of 3 types of missions, and are granted 3 attempts to complete them. In case your troops succeed, you are awarded 4 .
By default, you are pitted against a randomly picked player-owned army. Their Power can vary notably, from weak to overwhelming. Should you deliberately engage another player in Pick a Fight! session or be attacked by anybody else, this type of mission will feature your previous opponents depending on how often you fought, no matter what Power level you both are.
You have to exterminate a certain amount of rats, ever-growing with each new session you complete, up to the point when they are technically unable to be defeated. Rats engage in Melee only, but in a few days are capable to overrun your troops with sheer numbers, requiring a special approach for successful completion.
Your main army assisted by the best of your own recruits fight an assortment of non-playable troopers which usually outnumber yours by a notch and can carry more than 3 pieces of Equipment, but lack in levels after a couple of Waves. Because of the nature of this mission, you're not being offered one until you have a certain amount of recruits under your command.