Mercenary

Mercenaries are terran soldiers who fight for hire.

StarCraft II
In the StarCraft II: Wings of Liberty campaign, mercenaries are more powerful versions of basic units. Mercenary contracts may be purchased with credits from Graven Hill, a recruiter in Hyperion's. A mercenary unit may only be hired after its base unit is unlocked by playing the appropriate campaign mission. The War Pigs are the exception; they are hired free of charge after "Zero Hour".

During missions, a mercenary squad is trained at a merc compound. They have no build time, and arrive nearly instantly at the compound by drop pod. There is a short cooldown until the mercenary squad may be trained again. The squad size varies by the unit, and there is a limit to the number of squads that may be trained for each mercenary per mission. Mercenaries benefit from armory upgrades and lab research that benefit their base unit.

Mercenaries have unique unit models.