The first Targetmasters were a group of six Autobots under the command of Fortress Maximus. They had traveled to the planet Nebulos, they surrendered their weapons to the natives to prove their peaceful intentions.
When Lord Zarak and Scorponok had discredited the Autobots and turned public opinion against them, the Autobots had to retreat. A group of six Nebulan joined teh Autobots and allowed themselves to be bio-engineered into replacement weapons.
Vorath was able to duplicate the Autobots' experiment, creating a group of five Decepticon Targetmasters, though they were no match for the Autobot Headmasters. The Autobots left Nebulos to spare Nebulos further warfare, and the Decepticons pursued.
Some Transformers, known as Double-Targetmasters, are bonded with two smaller partners who can form individual weapons or combine with one another to form a 'double weapon', with the power of whichever weapon forms the 'barrel' boosted by the other.
The Targetmaster process was developed on Cybertron, as a process to forge a warrior and his weapon into a cohesive fighting team. The two are linked on a mental and physical level, allowing them to draw energy from each other work with extreme efficiency. Targetmaster weapons cannot be wielded by another being without their consent unless they are somehow incapacitated in their weapon configuration. Severe injury or death of one partner can have a profound physical and emotional impact on the other.
The Targetmaster process was further expanded upon on the planet Nebulon. This would allow organic humanoids, not just mechanoids, to function as weapons when adorned with removable armor. The strength and endurance of these modified beings were greatly enhanced, though their appearance does not change.
The Targetmasters were created by Hasbro and Marvel for the Headmasters (1987) series and Toyline. They were first seen in The Transformers: Headmasters #4 by writer Bob Budiansky and editor Don Daley.
Powers & Weaknesses
The Targetmasters benefit from being able to take two minds into battle. A Targetmaster possesses a living weapon that is capable of making its own tactical decisions and target priorities. The advantage is similar to that of having a dedicated gunner aboard an aircraft or tank. Unfortunately the Targetmasters themselves have not fighting abilities outside of being used by their Transformer partner.