Eggdome

The Eggdome is a bunker in New Megaopolis made for emergencies and is currently the main base for Dr. Eggman and the Dark Egg Legion after Enerjak destroyed most of the city. It is perfectly suited for housing about a hundred soldiers and also has all the necessary equipment for Eggman to build and test his machines.

Destruction of New Megaopolis
After Enerjak's destruction of New Megaopolis and all his forces, Eggman was forced to retreat into the Eggdome for cover, but left a short while later in response to Lien-Da who contacted him for an alliance to replace his troops. Eggman agreed, but Lien-Da was not made Grandmaster as she hoped. That position had already been filled by Dimitri as he proposed an alliance to Eggman first. Eggman also made sure they didn't rebel against him by placing bombs in the cybernetics he provided them with. (StH: #183, #184, #192)

Eggman's headquarters
When Sonic the Hedgehog and the Chaotix were attempting to destroy Eggman's communications tower, the D.E.L. had rush out of the Eggdome and into the field of battle under the command of Lien-Da and later Dimitri. They lost and the tower was destroyed, stopping Eggman from contacting half the continent. (StH: #189, #190)

Eggman later created a new robot in the Eggdome, a new Metal Sonic, that he could control and even speak through, to take down Sonic and the Freedom Fighters at Freedom HQ, only to find that it had been taken over by King Scourge the Hedgehog and his Suppression Squad. Scourge told him that he should leave, but Eggman decided to take out his wrath on Scourge instead. During the battle, Sonic arrived and it turned into a three way fight, and soon a two way fight when Metal Scourge arrived and Sonic and Scourge formed a temporary truce. Meanwhile, Dimitri confronted Eggman about why he had not yet made a new army of robots so the Dark Legion would no longer have to work with him and they could return to their lives, but Eggman said that he wanted to use the Echidnas until there were none left and that if Dimitri had any more complaints, he could discuss it with the bombs placed in the D.E.L.'s cybernetics. Later back at Freedom HQ, Metal Sonic and Metal Scourge were destroyed by Sonic, Scourge and the Suppression Squad that was reluctantly used by Scourge. (StH: #191, #192)

While Eggman was building one of his next battle machines, the Egg Tarantula, he ordered Snively Robotnik to go away as he was doing nothing but sitting around thinking and not assisting him. After being humiliated by Lien-Da and a Dark Legionaire, Snively decided to perform a routine maintenance check on the Sub-Bosses as communications were still possible in the Eggdome even after the Chaotix's assault, which allowed Snively to come into contact with a Sub-Boss know as Regina F, who he became romantically attached to and started planning a rebellion with. (StH: #194)

Eggman and Snively then set about work on a new Metal Sonic this time equipped with a SXSU-401 engine that was capable of teleporting through zones. But before Eggman could give it its orders, Metal Sonic teleported away to Sonic's location in Moebius where he was fighting Scourge, causing the doctor to go into a fit of rage. That Metal Sonic was later destroyed by the combined efforts of Shadow the Hedgehog, Blaze the Cat, and Marine the Raccoon. (StH: #195, SU: #1)

Use in the Battle Against Sonic
While Snively was talking to Regina, Eggman ordered him to assist him in testing his latest machine, accidentally calling him by his birth name of Colin in the process. Snively quickly made jokes about his next invention being something ludicrous, but he was soon shut up when he that his "uncle" had created a pyrotechnic killing machine called the Egg Phoenix. (StH: #197)

The Egg Phoenix was soon put to use when the Freedom Fighters and Chaotix made an assault outside the Eggdome against the Dark Legion. Eggman piloted the Egg Phoenix and almost killed the D.E.L. when trying to kill the Freedom Fighters. Dimitri openly protested to this while talking to Snively in the Eggdome. He then told Snively that he knew about Regina and his plans and said he'd turn him into Eggman if he didn't see to it that the Dark Legion was kept safe, but Snively convinced Dimitri to keep his mouth shut by saying that they could both benefit from his and Regina's plan. Soon after, the Egg Phoenix was destroyed and Eggman ordered Snively and Dimitri to round up the Dark Legion for tomorrow's final battle. (StH: #198)

Areas

 * Dark Egg Legion's barracks: The D.E.L.'s barrack's is basically a large room filled with bunk beds for sleeping arrangements and also stores their Eggpods.
 * Communications Room: Basically just a room with many computers and monitors that allows Eggman to stay in contact with the rest of Mobius, although Snively is the only one that uses it in order to stay in contact with Regina.
 * Lab: Eggman's personal laboratory with all the necessary equipment for Eggman to build and test his machines. Eggman created the third and fourth Metal Sonic, Metal Scourge, and the Egg Phoenix in the Eggdome's lab.
 * Monitor Room: An area of the Eggdome that oversees outside it and was used by Dimitri and Snively to watch the battle between the Freedom Fighters and the Egg Phoenix.
 * Egg Network Room: Similar to the Communications Room, the Egg Network Room allows Eggman to keep watch on all his Sub-Bosses around the world via the Egg Network, but he has recently let them go unchecked and Snively found it impossible to reach them, with the exception of Regina in the D. Kingdom.