The Last Autobot was a powerful and legendary Transformer, known by some as the Soul of Cybertron, and as the Ultimate Warrior by the Decepticons. He could transform into a vast, jet-like spacecraft. He was created by Primus as the savior of his children after his death, which occurred in 1990 at the hands of Unicron.
Deprived of the sentience that had shaped it, Cybertron seemed to enter a stage of collapse, and all the Autobots and Decepticons left. Hi-Q, a Nebulan Powermaster who was currently possessed by the spirit of Optimus Prime, the mutant heroes known as the Neo-Knights, and their employer G.B. Blackrock were the only lifeforms left on the planet- or so they thought. One of the Neo-Knights, Dynamo, had formed a connection with the energies of Cybertron during the battle with the Chaos-Bringer, and was being wracked with pulses by those energies. Hi-Q helped him focus on them, and they were led to the source- the Last Autobot.
The ancient construct was awakened, and it used its re-creative abilities to transform Hi-Q into the new Optimus Prime. It also gave him a new version of the Creation Matrix at his core. The Last Autobot took the new Prime and the humans to the planet Klo, where they saved the Autobots and defeated the Decepticons. The current whereabouts of the Last Autobot are unknown.