A gargantuan Fortress Maximus was first seen in a Matrix-induced vision of future Nebulos by Optimus Prime.

Later in the same era, a more normal-sized Fortress Maximus was a co-leader of the Autobot forces on Cybertron, along with Ultra Magnus. As Cybertron's resources ran low, they struggled to hold the Autobot army together. The peaceloving Fortress Maximus decided to offline himself indefinately following the Micromaster revolt however. Micromasters (comic)