Master is an alien world cursed with murderously hazardous atmospheric conditions, which became home to a group of unfortunate Cybertronian refugees. Many technological advances resulted from the struggle to survive this protean hellhole, including Headmaster Transtectors.
RTM dub name: Master Star
Headmasters animated series and manga
Millions of years ago, during the Cybertronian civil wars, many groups of Autobots fled the planet in order to escape the wearying corrosion of war without end. One particular group of diminutive robots, so young as to not yet have even mastered transformation, wound up crash-landing on Master. Unable to repair their ship at the time, the group, led by Fortress, attempted to eke out an existence on Master, mining energy and constructing cities, but the planet's deadly weather conditions and seasonal changes - including sandstorms, whirlwinds, metal-searing acid rain, scorching heatwaves and, during the ensuing four million years, even two ice ages - claimed the lives of many of their number. Constant deadly peril has its bright side though, and the need for survival fostered many technological advances (aided in part by technology derived from a time-travelling spaceship that later crashed on planet), most notably the creation of larger, stronger, non-sentient Transformer bodies named "Transtectors" that could better weather Master's dangerous environments. However, to connect to these bodies, the Cybertronians would have to learn to transform, and so underwent a rigorous training process to master the skill, with the most adept eventually becoming the Headmasters.
At some point over the years, they redeveloped space flight, but, for whatever reason, never left the planet, perhaps because they had simply reached a point where they were comfortable and in control of their situation on the planet, and had made a home there. However, when several Headmasters under the command of Scorponok rebelled against the leadership of Fortress, they were forced off of Master, eventually joining up with Galvatron's Decepticons. The Decepticon ninja Sixshot is known to have visited Master before the inception of Headmaster technology, so he may have helped forge this team-up. Whatever the case, he and the Decepticon Headmasters returned to Master in 2011 to attack the Autobots there, before pulling out to join Galvatron in an attack on Cybertron. The Autobot Headmasters departed Master aboard Fortress's Battleship Maximus, pursuing their enemies to their home planet and teaming up with the Autobots there. Fortress and Scorponok eventually became the leaders of their respective factions, and the advanced technology that they brought with them from Master was responsible for resurrecting Soundwave and Blaster as Soundblaster and Twincast.
Life continued on Master, with more young Headmaster Warriors undergoing the training to perfect their transformation powers. Some time later, however, after being defeated on Earth, Scorponok's Decepticons returned to Master, and the young warriors formed a resistance force to battle them. It didn't go too well. A small group of refugees escaped from Master to alert the Autobots to their planet's plight, but after doing so, they were caught in a plasma explosion and fused to the arms of several Autobot and Decepticon warriors, creating the Targetmasters. Why the robots travelling to deliver this message were the only ones on the planet that seemed unable to speak actual words and had to communicate via Artoo-Deetoo/Mini-Con-like electronic beeps is unknown. Despite this handicap, the Autobots subsequently returned to Master to aid the resistance effort, but Scorponok had discovered G-Metal beneath Master's surface and used it to forge the Zarak Shield, with which he bested Fortress Maximus. Having claimed this victory, the Decepticons then immediately departed Master for their final attack on Earth.
TV Magazine Masterforce prologue
Following the failure of the Decepticons' attack on Earth, they were forced off the planet for good, and the war became space-based, with the Autobot and Decepticon forces operating on Athenia and Chaar, respectively. The advanced technology of planet Master formed the backbone of this conflict, which was dubbed the "Master Wars." The Transtector technology of Master was subsequently upgraded with the addition of Masterbraces to create the Headmaster Juniors, and was presumably responsible for the creation of the Godmaster Transtectors as well.