Aron originally dwelt upon the Watchers' home-world with the other Watchers. He observed Captain Mar-Vell and Rick Jones battling Mad-Eye, and then attended the trial of Uatu. Aron was seen alongside Uatu again later. Aron decided to forsake the Watchers' oath and actively participate in events on Earth, becoming an instigator and manipulator. He set Dragon Man against She-Hulk and the second Ms. Marvel, and obtained cell samples from the Thing and Ms. Marvel. Aron observed the Fantastic Four battling Graviton, and witnessed the events of Inferno. Aron was in turn observed by Necrodamus. Aron then joined forces with the Frightful Four against the Fantastic Four, but soon quit the Frightful Four. Aron created clones of the Fantastic Four and Ms. Marvel, and imprisoned the real Fantastic Four and Frightful Four members in suspended animation, and watched their dreams. He replaced the real Fantastic Four with his clones, and set them against the Mole Man. Aron continued to engineer "adventures" for his clones, causing them to appear as criminals. The clones battled the Avengers and Doctor Strange, and were ultimately defeated by the real Fantastic Four after the originals broke free. Aron settled for watching the dreams of the clones instead.
Once they learned of his disobedience, the other Watchers tried to bring him to trial, but he escaped. Aron came to hate humans, because one of them, Doctor Doom, stole a portion of his cosmic power. For a time he masqueraded as Uatu in order to manipulate the Fantastic Four.
When the entire species of the Watchers faced extinction at the hands of the Celestials, Aron planned to plunge either Earth's solar system or its galaxy (the narration is not entirely clear) into a pocket universe, which he intended to live on in. However, his plan was thwarted by the expanded Fantastic Four and their allies, and Aron was reduced to energy by his uncle Uatu. For this action, Uatu was stripped of his position as a Watcher, but it seems (and logically so) that his fellows have since reassessed the facts and reinstated him. As for Aron, Uatu believed that his energies would serve as the core around which to create a new "One", the sentient repository of all the Watchers' knowledge, whose predecessor had been destroyed by the Celestial Exitar.