In the first five years that they worked together on the Fantastic Four, Stan Lee and Jack Kirby combined to create many different worlds for the Fantastic Four to explore and many different villains for them to fight, so for the storyline leading to the fiftieth issue of the book, they knew they needed something special, something more than just a super villain. So what they came up with was Galactus, who was, effectively, God.
An almost omnipotent being, Galactus actually lived by draining the life from whole planets. He first came to Earth in “Fantastic Four” #48, along with his space faring herald, the Silver Surfer, with the intention of destroying the Earth so that he could feed.
For the first time since he formed the Fantastic Four, Mr. Fantastic could not come up with a solution. Their only strategy was to attempt to keep Galactus from setting up the machinery he needed to devour the Earth. Galactus, though, had defenses against such attempts, including Destroyer robots and his powerful herald, the Silver Surfer. In the ensuing melee, the Thing managed to knock the Silver Surfer clean across town. In the next issue, “Fantastic Four” #49, the injured Surfer is aided by the Thing's kind girlfriend, the blind sculptress Alicia Masters. Due to Alicia's kindness, the Surfer finds himself doubting Galactus' mission for the first time. Perhaps there is something worth saving on this planet.
Meanwhile, the Fantastic Four have no luck stopping Galactus' machinery from completing, so the cosmic being, the Watcher, who is duty-bound to only watch events of great importance, finds that he just cannot stay uninvolved, so he sends the Human Torch on a mission through space to find the one item that can stop Galactus.
In “Fantastic Four” #50, the final part of the Galactus trilogy, the Surfer, thanks to Alicia's kindess, has found a conscience. He is now determined to stand up for the people of Earth, and he turns on his former master and tries to stop Galactus, but Galactus is too powerful. The Surfer is tossed aside and the Earth appears doomed. However, the Surfer's defiance bought the Torch enough time to retrieve the device the Watcher sent him to find – the Ultimate Nullifier, a device that could erase the entire universe. A device that even Galactus fears.
After Mr. Fantastic threatens to use the device, Galactus agrees to leave the Earth alone and departs, but not before he punishes the Surfer by binding him to Earth, keeping him from ever soaring the celestial skies again.