Fortress Maximus is a supporting character in the Transformers franchise. The original version of the character is the protagonist of Marvel's Headmasters miniseries and the subsequent "Trial by Fire" storyline, and the deuteragonist of the Underbase Saga.
Fortress Maximus made his debut in the very last episode of "The Rebirth", the miniseries that closed the original cartoon. He was constructed by Spike Witwicky and Cerebros from an old Nebulan city, as a giant Autobot capable of transforming into a battle station, under their control as part of the Headmaster process. Fortress Maximus travelled to Cybertron where he battled first the similarly giant Scorponok and then the rest of the Decepticons, driving them off the planet. Afterwards, he returned to Nebulos.
Fortress Maximus was the leader of a unit of Autobots on Cybertron. He came to believe that the war with the Decepticons would never end so sought to remove himself and his troops from it. They travelled to the planet Nebulos hoping to live there in peace, only to fall victim to the scheming of the ambitious Nebulan Lord Zarak, who framed Maximus' emissary Blurr for an attack on their peace symbol. To convince the Nebulans of their peaceful intentions, Maximus and his top lieutenants removed their heads, deactivating themselves.
Although Maximus made an agreement with the peaceful Nebulan leader Galen, Zarak's machinations brought his old rival Scorponok and the other Decepticons to Nebulos. In order to fight them, Maximus and Galen worked with a scientist, Arcana, to develop the Headmaster process, where Nebulans were bio-engineered to become the Autobots' missing heads, with Galen partnering Maximus. Initially, this gave them the upper hand over the Decepticons, but then Zarak helped Scorponok and others undergo the same process. When a group of Nebulans were threatened, Maximus and the others prioritised saving them over fighting the Decepticons and were overpowered and captured. They were ultimately freed by Zarak, who realised the damage the Transformers' war was doing to his planet and convinced Maximus and Galen to lead the Autobots off Nebulos so the Decepticons would pursue them.
Fortress Maximus chose to head to Earth, having heard of another group of Autobots and Decepticons based there. He quickly made contact with Goldbug and Spike. He initially had no interest in aiding humans, even though Spike's brother Buster was a prisoner of the Earth Decepticons. However, he changed his mind and protected Spike from Scorponok. Galen was killed as a result and Spike replaced him as Maximus' Headmaster partner. Together, they led an attack on Ratbat's island base to try and rescue Buster. They failed, but did manage to defeat Shockwave, who was apparently destroyed.
After retrieving the disc containing Optimus Prime's personality, Fortress Maximus sought the aid of the Earth Autobots to construct a new body for him. However, current leader Grimlock saw both Optimus Prime and Fortress Maximus as threats to his authority and challenged Maximus to a duel. Grimlock's old rival Blaster volunteered to take Maximus' place but the duel was interrupted by an attack by Ratbat's Decepticons. Seeing the Autobots lacked clear leadership to combat them, Fortress Maximus sent Goldbug to Nebulos to seek help there to revive Optimus Prime.
The mission succeeded and the two Autobot groups united under Optimus Prime's command, with Fortress Maximus serving as his second-in-command. Early in his tenure, he joined a taskforce Optimus Prime set up to battle the marooned future Decepticon leader Galvatron, only to watch Optimus Prime and several others shunted into limbo by the arrival of Rodimus Prime's Autobots from the future. After initially fighting the newcomers, Maximus was convinced to join them, and also Scorponok and a group of future Decepticons led by Soundwave, to challenge Galvatron, although he was taken out of the battle by Galvatron's ally Megatron.
Afterwards, Fortress Maximus was part of the Autobot group who uncovered Starscream's plan to absorb the power of the Underbase. They joined up with both Ratbat and Scorponok's Decepticon groups to defend Earth from the now super-powered Starscream, only to see most of their number fall. Fortress Maximus was one of the few to survive Starscream's attacks before Optimus Prime finally tricked Starscream into destroying himself.
With Buster rescued during the incident, Spike resigned from the Autobots, leaving Fortress Maximus inactive. He was brought back online in order to save Spike from Decepticon assassins Carnivac and Snarler. Some years later, with the rest of the Autobots off planet, Spike reactivated Maximus again to battle Galvatron, defeating him.
In the Generation 2 comics, Maximus was again reactivated by Spike after Megatron returned and ended up sacrificing himself to blow up the Ark, which Megatron was using as his base, although he failed to take Megatron and Starscream with him.
Robots in Disguise (2001)
After being teased throughout the series, Fortress Maximus made his debut in an eponymous episode towards the end of the show's run. He had lain dormant on Earth for some time, programmed only to obey orders that were just and helped innocents. His power meant he was a target for both the Autobots and for Galvatron's Predacons. He had a special affinity with children, whose pureness gave them some control over him. To this end, Scourge kidnapped the young human Carl, a rival of the Autobots' friend Koji, and tried to use him against Galvatron. The scheme failed when Carl's sour attitude towards Koji caused Fortress Maximus to power down.
In the show's last episode "The Final Battle", Koji managed to convince several of the world's children to donate their powers to Fortress Maximus, allowing him to give Omega Prime an energy boost in order to triumph over Galvatron. After the incident, Maximus joined Ultra Magnus in transporting the surviving Decepticons and Predacons to Cybertron as prisoners.
Fortress Maximus was the base of Sentinel Prime and did not appear to be sentient. Its only appearance was in the third season episode "This is Why I Hate Machines", when Sentinel Prime tried to use it against Omega Supreme.