The Key to Babylon Garden is an ancient artifact that appears in the Riders Saga. It is a transparent cube with ancient symbols and markings. Originating from the Babylonians or possibly their early descendants, this ancient relic has been passed down from generation to generation of the Babylon Rogues since ancient times. Its purpose is to reveal the fabled Babylon Garden, the home of the Babylonians, from its hiding place and control the inner workings of this sanctum as well. Only the power of the seven Chaos Emeralds can activate it.
The true reason for the creation of the Key to Babylon Garden remains unclear. The Key to Babylon Garden's purpose was to reveal the location of Babylon Garden, reactivate it and bring it back into the sky where it belonged before it had fallen from the sky in the forgotten past. It also unlocks the many sealed doors that lay within this location. However, it required the power from the seven Chaos Emeralds in order to be activated, a fact that was apparently forgotten or left out by the Babylonians and/or their descendants.
The Key to Babylon Garden was one of the few things that remained in the possession of the descendants of the Babylonians after they scattered across the globe and had forgotten most of their history and knowledge about their ancestors over time. Eventually, the Key to Babylon Garden came into the possession of the possibly last group of Babylonians, the Babylon Rogues, an band of thieves, who passed it on from one generation to the next. The stories about the Key to Babylon Garden being able to reveal and open up for Babylon Garden, however, endured the test of time, since the Babylon Rouges continued to believe that their thieving ancestors had hidden valuable treasures inside Babylon Garden.
In the Riders Saga, the Key to Babylon Garden had been passed on to Jet the Hawk, the newest leader of the Babylon Rogues, by Jet's father, but he had no idea how to use it. Dr. Eggman, however, having discovered that the Babylonians' treasure inside Babylon Garden was actually advanced technology that he hoped he could use to conquer the world, wanted the Key to Babylon Garden for himself so he could use it to claim this treasure. Rather than stealing the Key to Babylon Garden, however, Eggman decided to manipulate the current Babylon Rouges who had the key to do his dirty work by having them collect the seven Chaos Emeralds, having somehow learned how they could activate the Key to Babylon Garden, and have them uncover Babylon Garden for him. As a result, Eggman sought out Jet, Wave and Storm and requested an meeting with Jet to talk about a proposition to help him find Babylon Garden. At first, Jet was wary to trust Eggman, but as soon as Eggman revealed how the Key to Babylon Garden could be activated with the Chaos Emeralds, Jet accepted his help.
To gather the Chaos Emeralds, Eggman hosted the EX World Grand Prix with the Chaos Emeralds as the price of admission to bring the emeralds into proximity of Jet and the key. The plan was then to have the Babylon Rogues, now working for Eggman as his contestants, win the tournament and claim the emeralds as their prize. Though Team Sonic entered the tournament to stop whatever plan they though Eggman had, Eggman had anticipated that.
At the end of the tournament, all seven Chaos Emeralds had been gather as the prize and Jet had the Key to Babylon Garden ready.