The Commander is a special unit that appears only in Terminate the Commander games. They are foot units with a lot of hit points, but with no attack. They cannot be trained, but every player starts with one.
Players in a Terminate the Commander game must keep their own Commander alive, while killing the enemy's Commanders. If the Commander is killed, the player instantly loses. All players also start with a Fortress, so players commonly garrison the Commander inside it.
Players can always find enemy Commanders by using the Commander Locate button at the Fortress. It costs 400 Nova, and temporarily reveals the position of all enemy Commanders on the mini-map. It is researched almost instantly, and can be researched again and again.