The Zodiac Key is a powerful mystical object from the Ankh Dimension and created by the Brotherhood. The Brotherhood’s dimension is said to thrive on conflict, especially conflict between the forces of good and evil, in which neither side entirely and permanently defeats the other. The Zodiac Key was designed to perpetuate this conflict and was sent to Earth, where the battle between good and evil is more intense than in their own world.
The Key appeared to Jacob Fury, drawn to him by his great potential for doing evil, motivated by his intense hatred of his brother, Nick Fury and of the society and governmental system that he worked to protect. Jacob used the Key in his guise of Scorpio, member of the Zodiac, and the Key would rotate among the Zodiac’s leaders according to their membership rules. After various confrontations with different heroes, the Key was once believed to have been destroyed after Aries was defeated by the Avengers and Daredevil. The Brotherhood could easily re-create the Key, however, and it soon found its way back to the Zodiac. This time, it was used to transport various members of the Zodiac and Nick Fury, Daredevil, Iron Man and Madame Masque to the dimension from which it originated. The people were returned to Earth, but the Brotherhood chose to retain the Key after revealing its origin.
In fact, the Brotherhood again sent the Key to Earth, specifically Jacob Fury, who discovered it in a pawn shop. He used it as an energy source for his "Theater of Genetics" to create sophisticated androids known as Life Model Decoys (LMDs). He created the androids to serve as members of his own Zodiac organization, but after their defeat by Nick Fury, the Defenders. and Moon Knight, Jacob Fury took his own life. However, the Zodiac Key, perhaps displaying it sentience for the first time, constructed an LMD in Jacob’s form. This LMD believed itself to be the original Jacob Fury and that the original Jacob Fury's spirit and consciousness were transplanted by the Key into this android form. The new Zodiac had several altercations with the Avengers, and should any of their members be killed, the Zodiac Key could immediately resurrect them. Claiming superiority and believing that the Zodiac would eventually kill the Avengers as the androids could never be stopped, Scorpio wanted to use the Key to transport everyone on the scene to the Key's native dimension where the conflict, he believed, could be prolonged indefinitely. However, when the androids were in the other dimension, they ceased to function because each of them were aligned with a particular zodiacal energy, energy that did not exist in the other dimension. The Avengers were sent back to Earth by the Brotherhood, but secretly the Brotherhood waited so that someday they could also send the Key to Earth again and create new conflicts for them.
Another Zodiac organization has arisen, making its public appearance by way of its member Scorpio. Scorpio, in possession of the Zodiac Key, claimed he was given the Key by its creators, the Brotherhood. Scorpio further claimed that there have been many Key-holders throughout history, including the Illuminati, but he is one of the so-called "Chosen."
Scorpio made his appearance by using the Zodiac Key to unlock the balance between chaos and order, splitting the cosmic being known as the In-Betweener into his two diametrical halves and keeping the chaos-side in the Brotherhood's realm. The Avengers investigated, thwarting Scorpio's plans by reuniting the In-Betweener. The In-Betweener recognized the Brotherhood's dimension as a place of his own creation, one formed for his own sanctuary but had grown a life of its own. The In-Betweener cleansed the dimension, destroying what seemed to be the Brotherhood and undoing Scorpio’s schemes. Scorpio returned to a new Zodiac, claiming that he fed false information about his motives to the Avengers. The entire scheme was a plan to gather data on the Avengers on behalf of the Zodiac.