What is better than a Combat Drone? Three Combat Drones! Increases the maximum amount of concurrently active Combat Drones. In addition, summoning Combat Drones no longer costs energy and Drones have increased attack-speed.
combat drones: maximum count +2 combat drones: no longer costs energy combat drones: increased attack-speed 1000 minerals
This Mastery costs 2000 minerals to activate in addition to 1 Mastery point.