Players start the game with two workers and can purchase additional ones by spending gems or buying special packages. As a resource, workers cannot be attacked or lost.
Every time you want to upgrade, dig, or build something, you need to assign a free worker for construction. As soon as you complete the job, the worker becomes free again, and can be assign to a new job. Until then, the worker is unavailable and can only be freed up by completing the job, which can be finished instantly by spending gems.
NOTE: You can buy workers at a 20% lower price during events such as 'Boost Your Defense' or 'Boost Your Castle'.