Crisis City

Crisis City is an action stage in Sonic the Hedgehog which, as said in the game, is at least 200 years in the future. It was destroyed by a monster named Iblis and all that's left are ruins of buildings and streets. The only known living people there are Silver and Blaze, although there have been mention of others by Silver. Judging by what Silver says, it seems that the other inhabitants of the future seem to have evolved psychic powers similar to Silver's to survive, but none are seen to confirm this. Other inhabitants are monsters spawned from Iblis. The origin of the city is unknown, though it seems likely that the city is the ruins of Soleanna.

Sonic
As Sonic, you start off using a board to get through part one. Then you run through the level after that. After that you appear in debris flying through the air. After that, Sonic goes through a super-speed area. After locating a database stating the destruction of the Egg Carrier and Elise's death, you go to Flame Core.

Shadow
As Shadow, you start off in an optional armored buggy. After that you can grind and run through the level. And after that you are in an air glider flying through the debris of the city. After locating the green Chaos Emerald and finding an inoperable Omega, you go to Flame Core.

Silver
As Silver, you start off hurrying towards Iblis. Then, you play as Blaze to attack the monsters and hurry towards Iblis. Then you're Silver and hurrying towards Iblis again. After that you fight Iblis.

This is the first level in Silver's Story.

Tails
This is the first section of the End of the World, and Tails has to find the yellow Emerald.

Overview
While Crisis City's origins are not explained, it is presumed that the city was destroyed in the release of Iblis in an alternate timeline with the death of Princess Elise, caused by the Iblis Trigger. The city is in ruins, and mostly on fire due to Iblis' neverending destructive flames, although a lot of buildings are still standing.

In one of the several alternate timelines of Sonic '06, Princess Elise was captured by Doctor Eggman to obtain the power of Iblis, but in the process, the aircraft the two were in lost power and crashed, killing them both and presumably releasing Iblis, although it is possible that the Iblis Trigger caused the release of Iblis, due to Sonic the Hedgehog attempting to rescue her.

Following Iblis' release, the world was thrown into an apocalyptic state, Iblis destroying most places including Crisis City. Mankind blamed Shadow the Hedgehog for the destruction and imprisoned him with assistance from E-123 Omega who later shutdown and went into emergency stasis. Silver, determined to discover who or what caused the world's destruction and Iblis' release, is visited by Mephiles the Dark who informs him and Blaze that it was Sonic who released Iblis and is the Iblis Trigger. He then proceeds to send the two into the past to stop Sonic, but Mephiles himself is in fact the Iblis Trigger.

At the same time that Silver and Blaze meet Mephiles, Sonic, Miles "Tails" Prower and Knuckles the Echidna arrive in the city, along with Shadow and Rouge the Bat who meet up and then separate to search for the Chaos Emeralds in order to return to the past using Chaos Control. Sonic, Tails and Knuckles witness the talk between Silver, Blaze and Mephiles and access an old computer, revealing Elise's death and Iblis' release, prompting them to return to the past. Shadow sends them and Rouge back to the past before facing Mephiles, who revealed what happened to the Ultimate Lifeform. Omega is sent in by Rouge to help Shadow defeat Mephiles and return to the past.

Later, Shadow, Rouge and Omega return to the future to battle and destroy Mephiles for good, defeating him but reducing him to a liquid state. Silver and Blaze return to Crisis City, and battle Iblis. Iblis is defeated, and Blaze becomes Iblis' new host, seemingly sacrificing herself to bring peace and sunlight to Crisis City, extinguishing Iblis' flames.

Due to Elise blowing out the flame that Solaris originated from, all events regarding Iblis, Mephiles and Solaris were erased, so Crisis City's apocalyptic state likely never occured. However, in Sonic Rivals 2, Silver states that his future is decimated because of the Ifrit.

Trivia

 * In some areas of Crisis City, there are ruined road signs with directions to Central Park on them, suggesting that Crisis City could be New York City in the future.
 * The music for Crisis City bears a strong resemblance to Super Mario 64's Koopa Road theme.
 * In Silver's stage, a few signs have faded writing with the writing "Chao Garden" on them. This could be a reference to the Sonic Adventure games.
 * This stage will be reappearing in upcoming video game Sonic Generations.