Missions
Using gold you may conduct missions, either on your own kingdom to recruit workers, or on other kingdoms to find sensitive information (such as their armies whereabouts, or units they own). Sometimes, missions may fail, returning no results at all.

Missions: Recruit workers
Recruiting workers from within your own kingdom is a good idea early on, whilst you still have relatively few workers. Choose the amount of gold to invest, and try the mission. Sometimes you may find large amounts of workers, and sometimes you will find none. As your overall size and power increases, the best way to obtain more workers is by stealing them from another kingdom (see Units: Slavers).