The other is an alien consciousness from a far off dimension. It threatens all life everywhere.
The Other have been experimenting on the people of Earth for years. Some known abductees are Henrietta Rose and Stan Lee. Those coming in contact with the Other have no memories of the events but have certain familiar feelings about them.
The Silver Surfer was sent to investigate a familiar feeling that Galactus once had about the being. When he arrived he was able to fight them off and save Henrietta, but he obtained no memory of the event. During this time, some mental blocks were placed in the Surfer's mind.
One day, the Surfer was hit with a beam and lost his emotions. In a quest to find out why he discovered the blocks. He was sent back in time by the Clay Surfer to discover the reasons behind this. He went to Zenn-La and made his discovery. Galactus and himself from the past had been defeated by the Other. He then found that The Other had destroyed Zenn-La and all it's inhabitants.
Back in his own time, the Surfer had a sense of The Other's presence. He found them again attacking Henrietta. He stopped them and through her he learned of the true nature of this being. He went to face it but was easily defeated. He was given a virus of the soul that threatened to kill him and everyone on Earth.
Alicia Masters attempted to help the Surfer by taking him to Agatha Harkness. Even her vast magical abilities were no match for the Other. It was only when the Scrier intervened was he cleansed of this virus, but it cost him his life. He was resurrected and he and the Scrier went to bar the being from their reality. They traveled to the Nexus of All Realities and found the domain of the Other. Combining their powers they were able to create a barrier to hold The Other in it's own dimension.
Years after, Scrier borrowed the Silver Surfer from Galactus, who were once more master and herald, and went to stop The Other, who found a way to free him self from the barricade. Meanwhile Thor was driven to the Other by Rachel, a friend of him. This latter was an entity made of Scrier's thoughs disguised as a human, in order to lure Thor into The Other's hand. This was Scrier's plan to win a truce of half billion years with the Other. It is when Thor has accepted to scrifice him self for the good of the universe, that Galactus acted to stop the Scrier's scheme, and went in a cosmic battle with the two rival entities. The clash between the three powerful beings was so immense that space and time were bent to the breaking point, reality itself was endangered, but thanks to the great effort of Thor, the Silver Surfer and Rachel, they succeeded to stop them and make them realise the acuteness of their fight.
Finally, the truce was made between the Other and Scrier. For now at least.