Eggman's World Conquest
After getting ahold of a mysterious artifact known as the Phantom Ruby, Dr. Eggman began preparing for what he assumed would be the final battle. Eggman successfully defeated and captured Sonic and conquered the majority of the planet. This city served as one of Eggman's main territories during this time. When he lost the war to Sonic and the Resistance, this city was left in ruin. (StH: #1, #7)
After the War
Imperial City was once a city filled with technology. Now, however, it lies in ruins and is filled with nothing but wreckage.
- According to writer Ian Flynn in a post on Twitter, the name of the city comes from the location, Imperial Tower, from the Sonic the Hedgehog video game series where it first appeared in Sonic Forces which was located within Eggman Empire Fortress. The city itself is a more general location where the Imperial Tower was located.