Many years ago, his spaceship crash landed on earth.It imbedded itself on the bottom of the sea and he was unable to free it. When he searched for help the humans feared and attacked him so he used his Ray Gun to turn the attackers to stone. Captain America after hearing this story believed him to be the legend of the Medusa.
Many years later he asked Namor for help and in return he had to turn the Avengers to stone while at a press conference.
Captain America was not turned to stone, and with the help of Rick Jones, he tracked down the Alien.
Once he had confronted the alien he offered the Avengers help in return for the alien to restore them back from being stone.
Once restored the Avengers took him to his spaceship at the bottom of the sea and Thor helped bring the ship up far enough for him to make repairs. After his repairs were done he departed Earth in what seemed like an underwater earthquake which scared away Namor and his forces.