These four Autobots made their first appearance in the Earth year 2007. They were on Cybertron, along with Arcee, Blurr, Hot Rod, Kup, Cerebros and Sureshot, Crosshairs and Pinpointer, when Galvatron led the entire Decepticon army in an attack on Autobot City, and stole the Key to the Plasma Energy Chamber. Optimus Prime sent a warning to them that the Decepticons were on their way, and it wasn't long before the Decepticon mothership arrived, and the attack began. As the Aerialbots were felled by Sixshot, Scourge took the Plasma Key and headed for the Energy Chamber. All the Autobots named above, along with Spike and Daniel Witwicky, headed after him in a shuttle. Scourge opened the chamber, but was immediately overloaded by the energy released. Cerebros and Spike reclaimed the key, but then, the Plasma Energy overloaded their shutle's engines, and sent them careening through space, moving at a million miles a second. They eventually crashed on the planet of Nebulos, and were captured by a band of the planet's natives. These Nebulons were actually rebels, who were fighting against the Hive -a group of ten rulers who controlled the entire planet, using machines to enforce their evil will. The Nebulons nealy destroyed the Autobots with magnetic bombs, but the Decepticons, following the shuttles particle trail, arrived to disrupt the proceedings. In the ensuing battle, Blurr, Kup, Hot Rod, Sureshot, Crosshairs and Pointblank were captured, and Daniel was fatally injured. The Autobots realised that an interaction between Nebulons and Autobots would allow them to defeat the Hive, and to stop the Decepticons. So, they employed a theory formulated by Brainstorm - the removal and converstion of the Autobots's heads into exo-suits for the Nebulons to wear, effectively bonding the Nebulons to the Autobots, each sharing the others thoughts and powers. Cerebros, being a pacifist, refused, while Arcee took Daniel on as her partner. Thus were born- the Headmasters!

BRAINSTORM

Brainstorm's pet project, before the Nebulon fiasco, was implimenting a bonding between organic beings and Transformers. The Autobots' interaction with the Witwicky family over the years had proved that Autobots functioned better when aided by human partners - but Brainstorm's problem was finding out where they would inhabit the Autobots when they were in robot mode. After crashing on Nebulos, and learning of the Nebulan rebels' plight, everyone agreed that Brainstorm's theory sounded better and better. With aid from Spike, the Autobots detatched their heads, and had them converted into transformable exo-suits for the Nebulan strategists to wear. Brainstorm became partners with Arcana.

Brainstorm transforms into a futuristic jet. It is most likely of Cybertronian design, rather than a futureistic Earth desgin. In both this mode and robot mode, he is armed with a set of twin high energy pulse cannons. Arcana can sit comfortably in his cockpit in jet mode to help in piloting him, while becoming his head in robot mode.

CHROMEDOME

Chromedome is bonded with Stylor, an egotistical Nebulan strategist, who's more concerned with his appearance than war. Chromedome transforms into a Cybertronian car, and has hood-mounted infra-red sensors, which automatically target the set of roof-mounted twin blasters that he also uses in his robot mode. Stylor can journey within Chromedome when he's in vehicle mode, and, like all Headmasters, forms his head when he transforms to robot mode.

HARDHEAD

His name says it all! Hardhead's often reluctant to go along with the plans of others, and the only way to get him comply is often to convince him he thought up the idea himself. Like his Nebulan partner, Duros, who transforms into his robot head, Hardhead loves war more than anything else. In his Cybertronian tank mode, he has a 120mm cannon which fires sonic, incendiary and stun shells, while he is armed with two scatterblasters in robot mode.

HIGHBROW

A self-righteous snob, Highbrow finds warfare barbaric, and worthy only of the primitive. He prefers to talk about his ideas, but he uses an overdeveloped vocabularly to deliberately confuse others. He is bonded to Gort, the leader of the Rebel Nebulans, and transforms into a Cybertronian helicopter, equipped with radio jammers, radar, and magentic, infra-red and audio sensors. In robot mode, he uses two a pair od twin corrosive acid "rainmaiker" rifles.

With their new Nebulon partners, the Autobots were able to recover their lost companions from the clutches of the Decepticons, thanks to the Nebulons knowledge of the planet and its dangers. Shortly thereafter, the small group of Decepticons fell in with the Hive, and replicated the Headmaster process with five of their number, creating the Decepticon Headmasters. At the same time, the remaining Hive members and Decepticons underwent another form of bonding - the Decepticons reconfigured their weapons to transform into exo-suits for the Nebulans, becoming Targetmasters. When the Autobots were defeated by them, the Decepticons reclaimed the Plasma Key, and worked with the Nebulons to build a giant Headmaster City - Scorponok. The Autobots replicated the Targetmaster process with the remaining Nebulan rebels and Autobots, but the Plasma Key was already returned to Galvatron, who had constructed giant rocket boosters on Cybertron's surface, which propelled the planet into Earth's solar system. Galvatron planned to open the Plasma Energy Chamber and direct it's energy into the sun, causing it to go supernova, destroying Earth, Cybertron and the Autobots in the process. Spike and Cerebros worked together to rebuild an old Nebulon city into a new giant Autobot Headmaster City to fight Scorponok, in turn becoming bonded to each other. Spike became Cerebros's head, and Cerebros became the head of the new city - Fortress Maximus! Fortress Maximus bested Scorponok, and was then able to rerout the surplus energy from the sun back to Cybertron, re-energising the planet and restoring it's Golden Age. Energy backlash from the chamber blasted the Decepticons across the galaxy.

The Autobot Headmasters bore witness to the restoration of the Golden Age, and were presumably able to live in peace on the planet for some time. Brainstorm's interest in the benefits of a technological and organic merging may mean he had some had in the creation of Protoform technology. The status of any of the Headmasters at the time of the Beast Wars is unknown, though their Nebulon partners must surely be deceased.