Valeria: Card Kingdoms - Expansion #3 "Agents"
In Expansion Pack #3: Agents, you'll discover a whole new mechanic that will amplify your progress in the game.
Shuffle up the Agent cards and place them above the left-most Monster stack, then deal one Agent card face-up above each of the other 4 Monster stacks.
As an action, you can Hire one of the face-up Agents and use the power shown. Once you've completed the action, place the Agent face-down at the bottom of the Agent deck and refill the empty space from the deck. Agents will eventually reappear in the line for you to Hire, so you can plan some of your strategy around them coming back up!