One day, Sonic is showing off to his friends Tails, Amy, and Knuckles. All of a sudden, there is a great tremor and a loud crack, startling the team. Seconds later, Tails hears the radio announcer say that the earth has been split open again. Sonic, suspecting that Eggman is behind it like the first time, begins his trip to Metropolis, but is attacked by a large Gaian monster, which he is surprised to see in the middle of the day but defeats it quickly. Just then, Sonic sees Shadow a little ways away and runs up to him and asks him what he's doing. Shadow explains that he was following the trace of an energy signal somewhere in the ocean. Sonic offers to help, but Shadow quickly bypasses and says he can do it on his own. Sonic follows him anyway, but loses him at the beach. Sonic seaches for a while but is unable to find Shadow, convincing him that he'd already headed out to sea. But before he can begin his run across the sea, Sonic is stopped by Silver, who explains that he has come from a once-again ruinous future. After Sonic explains to him the details to Silver, the two decide to split up. Sonic goes out to searchat sea, while Silver stays to search on shore.
While Silver is searching, he comes across a small creature who happens to be Light Gaia ( aka Chip). He explains to Silver who he is and about the events from Sonic Unleashed. Silver recalls Chip's name being mentioned in Sonic's explanation. Chip then tells him that Dark Gaia is beginning to reawaken by itself, but is having trouble because of its last encounter with Sonic. Silver realizes that Sonic and Shadow must be headed straight to where Dark Gaia was rising, so he, along with his new friend Chip, go to warn Sonic and Shadow before it was to late.
Meanwhile, after searching the ocean thoroughly, Sonic finally finds Shadow in an abandoned ship, battling another Gaian monster, this one more powerful than the one Sonic encountered. After Sonic helps Shadow defeat it, Sonic begins to explain to Shadow about Dark Gaia but is inturrupted by Silver, who comes flying in with Chip. But before Silver can explain anything, there is a great explosion from beneath them, sending them all flying in different directions.
When Shadow wakes up on the beach, he sees Eggman a little ways away, holding Chip. Shadow doesn't know who he is yet, but recognizes him as the little creature who was with Silver and decides to help him so he can give him some answers. But before he can reach Chip, Shadow is spotted by Eggman, who panics at the site of him and summons an enormous robot to keep him busy. But Shadow defeats it quickly and catches up to Eggman, freeing Chip and forcing Eggman to explain what was happening. Eggman says that he was just trying to stop Dark Gaia from arising and was going to use Chip to do it. Shadow doesn't believe him at first, but Chip concludes that Eggman was telling the truth. Then Chip explains again to Shadow about what was going on. Just then, Shadow hears a loud rumbling in the distance. Immediatly then, Silver and Knuckles come in from above and tell Shadow and Chip that Angel Island is under attack. Shadow says that he's sure that Sonic is already on his way there. So he, Silver, and Chip prepare to head for the island, but are stopped by Eggman, who surprisingly gives them a Chaos Emerald. Then Shadow uses Chaos Control to warp themselves to the island, where they find several Gaian monsters and Sonic. After Chip once more explains what was happening, Sonic Shadow, and Silver prepare to defend Angel Island, there is another great rumble, and Dark Gaia rises from beneath the Earth's crust, only it is in its weaker form. Sonic, Shadow, and Silver fend off the beast by atttacking its eyes, but are unable to defeat it, as it only reheals itself every time it is injured. Eventually, it decides to absorb power from the Master Emerald. To keep this from happening, Shadow goes for the Emerald also to use Chaos Control and take it out of Dark Gaia's reach. The two touch the Emerald at once, and Shadow's Chaos Control reacts with Dark Gaia's power, zapping the beast and creating a wormhole that sucks in Dark Gaia and the Master Emerald, causing Angel Island to fall into the ocean. Chip concludes that the wormhole leads to the world of Dark Gaia, which is where all of Dark Gaia's servants live. The three hegdehogs decide that it's best to enter the wormhole and retrieve the Master Emerald before Dark Gaia.
When the team enters the wormhole into Dark Gaia's world, they end up having to battle numerous monsters until they find the Master Emerald. They all touch it at once, including Chip, causing it to give off a bright flash of green light, and before the team stands Tikal the Echidna. She explains that the Master Emerald released her because Sonic, Shadow, Silver, and Chip were all connected. Then she begins to tell of a legend of an incredibly powerful hegdehog that happened to be the true Light Gaia. His family knew what he would eventually have to do, so they spent most of their time training him to use all of his abilities, when to use them, and how to use them to his advantage. The lesson they always taught him was to enjoy life while he could, but to be serious when the time was right.
Then, when the young hegdehog( his name had become Ultima the hegdehog) had reached the age of 15, Dark Gaia awoken. But unexpectedly, it stole the Master Emerald and took in a great fraction of its power, causing it's body to dispurse into a spirit known as Pure-Dark Gaia. Although the beast was twice as powerful as himself, Ultima challenged it to a battle. The battle was long and perilous, but Ultima eventually defeated the powerful spirit.
But Pure-Dark Gaia was not finished. It created a spark with its fingers, which soon grew into Solaris, and was assigned to destroy( or at least weaken) Ultima. Although much weaker than Ultima, Solaris was still a super-dimensional life form like Ultima, which allowed him to rip him apart into different beings from different times, and sucked their power out and turned it into 7 Super Emeralds, which dissolved into Chaos Emeralds, and Chip, who had gained the title of Light Gaia. Believing that he had succeeded, Solaris concealed itself into a simple flame to rest, only to be destroyed by the three hegdehogs years later (although the three hegdehogs have no memory of these events).
Then Tikal explains that they were divided by their " symbolocy". Sonic stood for Ultima's present-self and his physical strength, Shadow stood for his past-self and his chaos energy( aka Chaos Spear, Chaos blast), and Silver stood for his future-self and his mental powers.
Finally, Tikal explains that Dark Gaia's servants were apearing in the daytime because they were fueled by their master's anger. And with that, Tikal leaves them to return to the Master Emerald. Shadow suggests that maybe she could tell them something more, but Tikal says that there's nothing she can tell them for now.
Just after Tikal returns to the Master Emerald, the team is attacked by another Gaian monster that grabs the Emerald, and Sonic, Shadow, and Silver battle for it. When the creature is defeated, Silver gets to it and uses Chaos Control to warp them back to their world. Once their there, they find themselves on Angel Island, causing the island to rise once again. Just then, Tails comes in from above and tells them that Dark Gaia has been spotted in Central City, so the team heads there to investigate.
When they get there, they find the city in chaos and swarming with Dark Gaian creatures. When the team find Dark Gaia, it they see that it has evolved somewhat into Semi-Perfect Dark Gaia. Sonic, Shadow, and Silver realize that they must defeat it before it reaches its final form, which they manage to do so. When they do, Dark Gaia falls and begins to slowly sink into the Earth, but the planet shows no sign of sealing its cracks. Silver says that mabye it is because Dark Gaia will continue to rise and be defeated, and Chip agrees.
Just then, as the team prepares to depart, Eggman shows up in a large mech with the Master Emerald. He feeds it to the sinking Dark Gaia and attempts to harnes its power but is blown away by the force from the explosion. Dark Gaia then tranforms into Pure-Dark Gaia and begins to dissintegrate the Earth.
As the planet slowly falls apart, everything seems hopeless untill Shadow pulls out the Chaos Emerald Eggman gave him and uses it to warp the other six to their location. Then the group decides that the only way to defeat the beast is to recombine themselves using Chaos Conttrol and recreate Ultima. As they all pick up an Emerald, they begin to glow brightly, and they tranform into Super Emeralds. And then, using Chaos Control, the three hegdehogs( and Chip) combine into Hegdehog Ultima, then begin to battle with Pure-Dark Gaia and manage to defeat it, causing it to blow up, returning everything to normal.
Afterwards when Hegdehog Ultima separates once again, Silver returns to his time, hoping that the future is bright once again. Knuckles takes the once again Chaos Emeralds and the Master Emerald back to Angel Island, while Shadow seemingly dissapears. Before Chip returns to the Earth to rest, he tells Sonic that they don't have to worry about Dark Gaia for a while. At the end of the game, it shows Sonic running off into the distance, looking for his next adventure.
Like most Sonic games, the game is played on a 3D-playing format. Each playable character can move in 8 different directions, along with the ability to jump, crouch, air dash, and slide. Players also have an energy bar in the corner of the screen that can be used for certain attacks. There is also a number of attacks for each character-
player attacks the nearest opponent
player continueously attacks nearby opponents
player tosses an opponent at another
player does a long-range attack that uses energy
player does an attack that destroys all nearby enemies and uses energy
player is powered up in some way that costs 10 rings and energy
Each playable character's attacks are unique, yet similar in some way-
Homing attack: homing dash
Combo attack: jump spin
Toss attack: double kick
Straight attack: spin dash
Defense attack: tornado spin
Super attack: light defense
Homing attack: teleport
Combo attack: flash teleport
Toss attack: chaos grab
Straight attack: chaos spear
Defense attack: chaos blast
Super attack: chaos control
Homing attack: telekinesis pull
Combo attack: telekinetic force
Toss attack: telekinetic throw
Straight attack: telekinetic push
Defense attack: telekinetic wave
Super attack: telekinetic field
There are seven zones on the world map, each with five normal acts( except the seventh zone) and one boss act.
Green Hill Zone
boss- Gaia Wolf
Death Yard Zone
boss- Egg Kong
Ocean Gravyard Zone
boss: Gaia Kraken
Angel Island Zone
boss: Dark Gaia
Gaia Dimension Zone
boss: Gaia Wizard
City Disaster Zone
boss: Semi-Perfect Dark Gaia
Gaian Devastator Zone
boss: Pure-Dark Gaia
Each stage has an assigned character, either Sonic, Shadow, or Silver. There are also certain stages where you can either choose a character or you must play as both or all characters at different points of the stage.
Special Thanks To
For giving me the idea of Chaos Unification.