Fortress Maximus was hidden on Earth ages ago to keep the planet safe—the idea being that he'd prevent some dangerous force from weaponizing humanity's raw potential. He went into hibernation beneath the surface with activation keys scattered globally: the O-Parts hidden in ancient ruins, the Orb of Sigma buried in a pyramid, and Cerebros stashed in a South American temple. Six Autobots were sent to reactivate him, but their ship crashed and they ended up dormant too, stuck waiting until the war between Megatron and Optimus Prime reached Earth.
Headmaster-wise, Fortress Maximus's head component was called The Emissary (Brave in Japan), and Cerebros served as the Emissary's own Headmaster—the smallest piece of the whole puzzle. Interestingly, the Japanese version made Cerebros human-sized while keeping the rest proportional to a normal Transformer, which made Brave Maximus absolutely massive compared to his American counterpart.
Megatron had his own reasons for showing up. He wanted to awaken Fortress Maximus himself, so he kidnapped archaeologist Doctor Kenneth Onishi, who'd picked up energy signatures from the sleeping giant and figured out where the O-Parts were hidden. While keeping Onishi sedated and mind-probing him for answers, Megatron didn't know the Autobots had planted a microchip with Onishi's son Koji to help them navigate. The search began in the Cave of the Dragon and continued from there.
Later, the Predacon Sky-Byte accidentally helped expose the O-Parts' importance when he took hostages and the Autobots, panicking, offered up the components as ransom—not realizing he had no clue what they actually were. The bluff backfired, but it led the Autobots to Fortress Maximus's body buried under the city. They unearthed it, hid it, and with Onishi freed, recovered the remaining five O-Parts despite constant interference from Decepticons and Predacons.
The seven O-Parts merged into a map pointing toward the Orb of Sigma, which then revealed the path to Cerebros. But the Decepticons grabbed Cerebros first. Scourge used a fragment of Optimus Prime's code to override Maximus's systems and trigger activation. The sequence went: Cerebros became the Emissary's head, the Emissary became Maximus's head, and suddenly this colossal Transformer was awake and rampaging—completely beyond Scourge's control until Koji told it to stand down. Maximus went back underground, leaving Cerebros in enemy hands.
Turns out Fortress Maximus was designed to respond to human commands, particularly from innocent minds like children. Scourge exploited his own latent human bio-signature to briefly control the giant, but a crowd of kids overrode him. The Decepticons then kidnapped Koji's friend Carl to use as a puppet master, which worked for a moment until Scourge, in a wild miscalculation, pointed Maximus at Galvatron instead.
When the Autobots finally got Cerebros back and understood the control mechanism, they brought Maximus online during a Decepticon assault. Maximus went toe-to-toe with Galvatron and nearly had him finished—at one point blasting apart the spaceship Galvatron had grafted himself to, crippling the tyrant badly. But Galvatron managed to drain Maximus's energy to restore himself, turning the tide at the last second.
Content compiled by AnimeList.moe from publicly available sources.
