- Why not check Sonic News Network for information on the original Eggman Empire?
The Eggman Empire (エッグマン帝国 Egguman Teikoku) is the capital that Dr. Eggman wishes to establish to rule the world from.
However, for now it is used figuratively by Dr. Eggman to boast of his political and military power.
Invisioned as a semi-automated industrial city with machinary as it's architecture, such cities have existed in the games such as Metropolis or Eggmanland which Dr. Eggman had favoured as his seat for his Eggman Empire.
Fanon
The Eggman Empire in others fanfiction.
Fan fiction
Sonic X the Remake
Eggman wants to build the Eggman Empire. He Invisions it as a semi-automated industrial city with machinery. Eggman uses it figuratively to boast of his political and military power. Once he built the Eggman empire, it took over Japan. The robots climbed up to the top of the Tokyo Tower and replaced the Japanese flag with the Eggman Empire flag. The Eggman Empire stretched from England to Japan.
BearfootTruck's Universe
In BearfootTruck's stories — mainly the ASMW series — the Eggman Empire is not just one city, but an entire country. When Sonic was five, Robotnik ousted the king & queen of Mobius in an aggressive coup. Together with his nephew Snively, they claimed the country for the Eggman Empire. He also resumed the war with the Roseinian Empire.
Robotnik's eventual plans are to expand the country to encompass the entire globe. However, there are two things in his way: First of all, the Roseinians are a very determined people, and even when outmatched in some way, they won't give up. Second of all, Sonic and his friends have been causing plenty of trouble for the doctor, preventing him from expanding much further.
Fan games
EN?GMA games
As in the games, so far it is the deluded goal and proud call of Dr. "Eggman" Robotnik. Still, Mystic respects those with large goals, just doesn't respect Dr. Robotnik and goal of world domination.
While Eggman has various bases of operations, most temporary, his home away from home is the Egg Carrier. Both Egg Carrier as well as Eggmans promise of his empire will be in Mystic Monkey Adventure and Ultimate Sonic. The Eggman Empire playing a more bigger role in the Sonic World, not only responsible for the robotisizing of the rare chao but also Dr. Eggman's guild is named after it.