Galactus traveled for eons, feasting on countless worlds and claiming innumerous lives along the way before arriving at the planet Zenn-La. Before he could devour the planet, he was contacted by a scientist named Shalla-Bal, who presented him an offer: should her planet be spared from his hunger, Shalla-Bal pledged to serve as his herald, finding planets for the Devourer to consume. Content with this arrangement, Galactus brought Shalla-Bal aboard his ship and granted her a fraction of the Power Cosmic, transforming her into the Silver Surfer. Guided by his new herald, Galactus consumed other planets, such as Saigas, Polaris and DA-773 before the Surfer laid eyes on a new mark. Upon reaching the planet LHS-275, Galactus consumed it, plunging his vessel through the core of the planet. Despite the best efforts of its crew to conceal their presence, Galactus took notice of an invisible spaceship, the Excelsior, and used a tractor beam to pull it into his own. Analyzing the group, Galactus detected the presence of a powerful being among them, and sent Shalla-Bal to fetch them.

Legends that predated Cybertronian civilization described Unicron as a dark god who consumed planets, but few knew of the legends, and fewer still believed them. The Maximals learned that Unicron was real only when the Chaos Bringer arrived on their doorstep to consume their planet. Unicron deployed his Terrorcon and Predacon forces led by his chief Herald Scourge, whom he had long ago enslaved. Unicron tasked them with finding the Transwarp Key, a Maximal device that would enable him to continue his rampage across time and space at will, before he consumed the Maximal planet. Unicron was livid with Scourge for losing the key as the Maximals led by Optimus Primal fled, and commanded Scourge to find the key. Though Unicron was still able to feast on the Maximal planet, he was left in the current galaxy, forced to rely on his own power to move about space, but this soon left him starving and desperate to find another planet to feast on.

This is your final warning: break the treaty again and you will be destroyed.

Scourge later found half of the Transwarp Key on Earth in 1994, but when he presented his prize to his master, Unicron scolded and tortured his minion as it was only half of the key. Scourge eventually retrieved the other half in Peru and began opening a portal in time and space for Unicron to come through. Unicron relished his apparent victory and made ready to devour Earth, but Primal and Optimus Prime's Autobots defeated Scourge and his other forces. When Prime made to destroy the portal, Unicron hastily offered Prime whatever he wanted in exchange for not proceeding, but the Autobot leader had none of it and destroyed the portal. Though Unicron had been stranded once again in his current location and time, the Autobots and Maximals acknowledged he had likely survived the collapse of the portal, but stood resolute that they would defeat him should he ever return to Earth.