Fifty years before the Space Colony ARK incident, a top-secret project known as "Project Shadow" had begun on the Space Colony ARK. Led by Professor Gerald Robotnik, it was a government-sanctioned initiative to create "The Ultimate Lifeform," an immortal being that could be used for the benefit of the nation, likely in a militaristic fashion. While Gerald had initial misgivings to the purpose of the research he was assigned to, he realized that his results might be able to save his granddaughter, Maria. Suffering from the incurable disease Neuro-Immune Deficiency Syndrome (N.I.D.S.), Maria only had a short time left to live, and Gerald was willing to do whatever it took to save her life. Going against his worries of stepping into territory man had no business playing with, the professor immediately began work, hoping that he could apply any newly-gained knowledge to find a cure to N.I.D.S.
Even with all the resources at his disposal, the professor was unable to make any significant progress. Without alerting anyone, Gerald decided to plead to the stars for help, contacting the Black Arms race, an alien civilization that lived upon the Black Comet, a celestial object that passed near the planet every fifty years. Its leader, Black Doom, offered to assist Gerald in his quest. He offered his blood - which ended up being the key to perfect the ultimate lifeform - in exchange for the seven Chaos Emeralds, which he would collect the next time he passed through. Knowing that the Black Arms' intentions were less than desirable, Gerald made the deal regardless, albeit with preparations to defeat the Black Arms with the cannon built into the ARK, and was able to successfully create Shadow the Hedgehog.
Once brought to life, Shadow immediately befriended Maria, and they became close during their short time together. Gerald, meanwhile, made precautions for the return of the Black Arms, ensuring that the Eclipse Cannon - an extremely powerful laser built into the ARK - was compatible with the seven Chaos Emeralds, so that when they did return with the Black Comet, humanity would be able to defend itself instead of bowing to their whims.
However, Gerald's progress was ruined when it was leaked to G.U.N. how he was able to create the successful prototype. During the meeting between Gerald and the Black Arms, one of the other children aboard the ARK had accidentally seen what transpired and reported back to those in charge. As ties between the ARK and the United Federation had already been strained, hearing the news of the dealings with an alien race scared those in charge. Afraid of the implications, it was decided to launch an invasion and put a stop to the work being done there.
What happened next was nothing short of madness, as G.U.N. troops descended onto the ARK, causing chaos and confusion wherever they went. Immediately they went after the Biolizard, which they thought was the successful "Project Shadow" prototype, and in the process of putting the creature into stasis, lost quite a few soldiers. From there they went about doing damage control, shutting down everything, getting everyone off the ARK, and killing those who resisted if need be. Knowing that the G.U.N. forces would be there at any moment, Maria convinced Shadow to enter an escape pod, her final wish to him that he give the people on the planet a chance to be happy. Wishing him goodbye, Shadow could do nothing as he watched the G.U.N. soldiers storm into the lab, firing a shot which would forever change the hedgehog's life as it ended the life of Maria Robotnik.
Learning of his granddaughter's death, Professor Gerald soon went mad with grief, swearing vengeance on humanity for taking away the only thing that ever meant anything to him. What is known is that both Gerald and the escape pod that held Shadow were gathered by G.U.N., Shadow having to be put to sleep in a stasis capsule within Prison Island, and Gerald being incarcerated and charged with the crimes that happened aboard the ARK. Before Gerald's incarceration and execution, he brainwashed Shadow, altering his memories of what Maria wanted of him as her final wish so that he would carry out his plan once he was awoken. Gerald then left a note behind in his diary that encouraged the reader to release Shadow if they wanted to cause global destruction.
In Sonic Adventure 2, Dr. Eggman set Shadow free from a G.U.N. base on Prison Island, where he had spent approximately fifty years in suspended animation. In exchange, Shadow agreed to aid the doctor in his plans to take over the world; holding to himself his true intentions as wishing to get revenge for the death of his friend, Maria Robotnik, as he thought she wanted; it is strongly implied that his belief that Maria's final wish was revenge against humanity stemmed from Gerald Robotnik modifying Shadow's memories between Maria's death and Shadow's encapsulation. To achieve this, Shadow revealed the Eclipse Cannon to Dr. Eggman, who later destroyed half of the moon in a demonstration to the populace. Beforehand, he also stole the green Chaos Emerald from a bank, unknowingly also framing Sonic the Hedgehog for the deed.
He later participated in the second heist alongside Dr. Eggman and Rouge the Bat against Prison Island, where he would plant explosives throughout the island as part of their getaway, although his resemblance to Sonic also resulted in Amy Rose mistaking him for the latter. However, because Tails came to Amy's rescue from Dr. Eggman, he was forced to act fast due to the unexpected delay. In addition, after Rouge ended up getting caught and stranded in the containment area while recovering the four Chaos Emeralds, Shadow, largely because he realized that his plans of avenging Maria Robotnik would be for naught if Rouge perished in the explosion, rushed to get to Rouge and by extension the Chaos Emeralds.
After meeting Sonic for a second time, Shadow also believed that Sonic was trying to copy him. They fought to a stalemate before Shadow was forced to leave to rescue Rouge (with Sonic also learning from Eggman via Shadow's radio that the island was about to blow up), and just barely arrived at Rouge's location and used Chaos Control to warp himself, Rouge, the four Chaos Emeralds and presumably Eggman out at the last possible second. After the demonstration, needing the final Chaos Emerald to fulfill their plans, Shadow pursued Tails' plane at a canyon. Although he was unable to stop them, he nonetheless reported to Eggman that they are headed his way. When Eggman discovered the presence of two apparent emerald readings, and thus deduced Tails' plan of placing a fake Chaos Emerald into the cannon, Shadow departed, apparently to confront Sonic and Tails to stop them for interfering, although Eggman stopped him, wanting to deal with them personally. After Sonic was seemingly killed by Dr. Eggman via a rigged escape capsule, Shadow, witnessing the explosion, guessed that Sonic was only an ordinary hedgehog.
Afterwards, Shadow stumbled upon Rouge's plan to steal the Chaos Emeralds, and deduced that she was in fact a spy for the President of the United Federations, although Rouge then unveiled a report from Gerald Robotnik regarding the Biolizard, claiming, it, not Shadow, was the actual Shadow. However, Shadow was forced to depart after Eggman mentioned an anonymous figure (Sonic) heading towards the Eclipse Cannon, although not before stating that he's still Shadow despite his memories possibly being fake, and that "the fake emerald is good enough for Rouge." He then discovers Sonic the Hedgehog at the area. Shadow, impressed at Sonic's capability of using Chaos Control despite using a fake Chaos Emerald, nonetheless stated that he cannot allow him to live before fighting on a collapsing bridgeway. In the last story, Eggman inserted the final Chaos Emerald, only to initiate a destabilization program on the ARK. Professor Gerald Robotnik then revealed that he had made this function to have revenge for Maria, and that the ARK would destroy the Earth. Sonic, Eggman, Rouge, Tails and Knuckles took a shortcut to the cannon's core so they could stop the Professor's mad plan.
Amy Rose then helped Shadow realize Maria's true wish. In a twist of fate, Shadow ultimately aided Sonic when realizing, with Amy's help, Maria's true wish, which was to save humanity. Meanwhile, Sonic the Hedgehog and Knuckles had reached the central core, where they reactivated the Biolizard. Notably, a scene from Gerald Robotnik's diary appeared again. After Shadow defeated the Biolizard, Knuckles used the Master Emerald to stop the Chaos Emeralds. But the Biolizard, being the prototype of Project Shadow, used Chaos Control to fuse with the ARK, continuing its fall. Then, Sonic and Shadow, in their Super States, destroyed the Biolizard. The Ultimate Lifeform prototype became a monster, codenamed Finalhazard. Using their powers, Shadow and Sonic defeated him and executed an enhanced Chaos Control which stopped the fall and warped the ARK. Afterwards, Shadow's energy was drained out and after falling to the Earth, he was presumed dead.
In Sonic Heroes, Rouge discovered Shadow unconscious in a stasis pod located in the deepest part of one of Dr. Eggman's bases, after he was believed to be dead. As she activated the capsule, E-123 Omega ban to scan Rouge and the newly awakened Shadow, believing him to be a creation of Eggman. As Shadow awakened, Omega fired a round of guns at Shadow and Rouge. Shadow ordered Rouge to step away while he tokk on Omega, but Rouge stepped in to break them up, quickly ending the skirmish. Shadow discovered that he has amnesia and could not remember anything before his release, aside from his name and brief images of Maria Robotnik's death. He unwillingly joined forces with Rouge and Omega, to form Team Dark and find Eggman.
On their way to Eggman on Grand Metropolis, Shadow and his team met up with Team Chaotix, and began fighting against them as Rouge suspected them to be searching for "Eggman's treasure". Later, Shadow met Dr. Eggman in a casino, asking him for his identity; however, "Eggman" denied that Shadow had "a past to remember". On another battle against one of Eggman's machines, Shadow discovered that there are clones of him, much to his already established self-confusion. After giving it a brief break, Shadow, however, chose to proceed forward. Unbeknownst to him, Neo Metal Sonic had collected Shadow's data while the hedgehog was fighting during that moment.
In Lost Jungle, Shadow confronted Sonic and his team of Knuckles and Tails. When they encountered each other, Shadow had no memory of Sonic, and asked Rouge about him. The two teams began taunting each other until Omega threatened Sonic and his team to destroy them. Shadow then started a fight against Sonic and his friends. When they made it to the Egg Fleet, Shadow made up his mind to defeat Eggman once and for all even if he was not truly the ultimate lifeform.
After "Eggman" was seemingly defeated, Shadow remarked that Rouge's desire to steal the Master Emerald from Knuckles as she was explaining her next plan is nothing strange for him. Shortly after that, Neo Metal Sonic revealed himself to them, and began transforming as Shadow, his teammates and the other teams were witnessing that moment. Having no other option, Shadow worked with everyone else to help defeat the monster, and gladly gave his Chaos Emerald to Sonic. After the final battle, Shadow and E-123 Omega were holding the defeated Metal Sonic.
In Shadow the Hedgehog, while being haunted by the thoughts of his past memories, Shadow witnessed an alien race known as the Black Arms arriving on Earth to invade, where the leader of the race, Black Doom appeared before Shadow and told him to bring him the Chaos Emeralds "as promised" before disappearing. Fueled with the desire to seek out his past and find the truth behind Black Doom's words in hopes of uncovering his past, Shadow sped off to obtain the emeralds. Depending on the player's actions, Shadow goes through several possible paths that each contradicts each other.
After successfully gathering all of the Emeralds, Shadow was confronted by Black Doom, who commanded him to give up the emeralds so that they could begin the "prosperity ritual". Sonic the Hedgehog and the others, including Dr. Eggman, then arrived and told Shadow not to listen to the alien leader. After it was revealed that Black Doom wished to harvest humans as an energy source, he took the Chaos Emeralds from Shadow and used Chaos Control to warp the Black Comet down to the surface of the planet. Black Doom then explained that he helped Professor Gerald create Shadow, but only in return for the Chaos Emeralds, which were needed to bring the comet down to the surface, before he paralyzed everyone with a special gas and left them to be devoured by his alien offspring. Due to having the same blood as Black Doom, Shadow was the only one not affected by the gas and continued forward as he finally put his past behind, swears to never let anyone manipulate him again, and is determined to destroy Black Doom.
Black Doom fled, leaving behind Shadow, the only hope for the planet. Shadow caught up with Black Doom and suddenly was attacked by mind control. Black Doom told him that he could control him as they had the same blood running through their veins. Just then, Team Chaotix activated a film showing a sane Professor Gerald Robotnik sometime before the raid on the ARK. In the video, he told him that he was the only hope for the planet. It was revealed that the only way to defeat the Black Arms was to destroy the Black Comet using the Eclipse Cannon. As the video ended, Maria stepped into the frame and gave Shadow the inspiration he needed to break through Black Doom's control. Black Doom escaped and prompted Shadow to use the Chaos Emeralds to become Super Shadow and fight the alien leader. Black Doom, now in his Devil Doom form, fought Shadow but was defeated. Shadow then used a super-powered Chaos Control to warp the Black Comet back into the planet's orbit and tear it apart with a blast from the Eclipse Cannon. Onboard the ARK and with the world now safe, Shadow looked at a picture of Maria and Gerald before tossing it away, resolving to put his past behind him and move forward with his life.
In Sonic Battle, Shadow tries to convince Sonic that Emerl is a threat, but Sonic refuses to believe him, forcing Shadow to fight Sonic. Sonic wins, but Shadow still warns him about the unknown dangers the "Gizoid" represents. Rouge the Bat saves Shadow while they are investigating Dr. Eggman's secret base and takes him back to her home. Shadow talks about how the people of Earth must destroy him and Emerl if they ever want peace, still believing that he is a weapon. It is revealed, however, that he ultimately has the heart and soul of Maria Robotnik, implying he could not be the enemy of humanity.
In the 2006 game Sonic the Hedgehog, Shadow is a playable character and has his own storyline and a new enemy called Mephiles the Dark. In this game, his story intertwines with those of Sonic and a new character, Silver the Hedgehog. In this role, Shadow is requested by G.U.N. to go to Dr. Eggman's base at White Acropolis to rescue their agent (Rouge), who was last contacted 26 hours prior. After storming the base and taking out the robots in the outer perimeter, he started the mission upon being briefed. However, by the time he arrived at the main gate, he encountered Rouge who at the same time opened the gate, to which he explained to a surprised Rouge that he had orders directly from the President to rescue her. Afterwards, Shadow was asked by Rouge whether he wanted to know what she was sent to retrieve. Shadow did not care, as he was only sent to rescue her. On the way to the extraction point, they were ambushed by several Eggman Robots, including the Egg Cerberus.
Upon arrival, he learned the history of Kingdom Valley, including the Solaris Project. He and Rouge encountered the new villain, Mephiles the Dark when the Scepter of Darkness falls and shatters (as Shadow rescued Rouge from freefall when she and the scepter were knocked away by Eggman). Mephiles, who had been sealed inside the Scepter of Darkness, was subsequently released with the relic's destruction, adopting Shadow's appearance due to absorbing his shadow. Shadow was confused by Mephiles' familiarity with him before the villain sent him and Rouge to the future as part of "a one way ticket to oblivion." Shortly after assessing their situation, they encountered Sonic, Tails, and Knuckles, who had themselves been transported to the future by Eggman. After explaining their shared predicament, Shadow then told Sonic that the only way to return to the present is to find two Chaos Emeralds and then perform Chaos Control together. Shadow and Rouge then found the Green Chaos Emerald but also discovered Omega's husk. Shadow then discovers that Omega's on standby mode. As they are unable to do anything for him, Shadow and Rouge reluctantly leave Omega behind. They then rendezvous with Sonic's group. Upon discovering that another Chaos Emerald was near the volcano, Shadow and Sonic proposed to locate it. Upon finding the Chaos Emerald, they fought Iblis, a fiery monster within the volcano. After the dispatching of the monster, Shadow proceeded to use Chaos Control with Sonic, opening a wormhole to their present. Before Shadow could follow after Rouge and the others, he noticed Mephiles' presence nearby and pursued him instead. Shadow followed Mephiles to a volcanic platform and questioned the demon whether he was responsible for the world's destruction. Mephiles showed the Shadow of that time period, held in stasis, revealing that in the aftermath of Iblis' destruction of the world, Shadow had been labeled as the enemy of mankind due to his perceived role in the disaster and their fear of his power. Despite the shock of this revelation, Shadow refused to join Mephiles, informing him that he "controls his own destiny." He fought Mephiles to a stalemate until Omega, who had awakened to fulfill Rouge's request from the present to aid Shadow in the future, intervened. The two then chased after Mephiles upon his defeat, returning the present, but he escaped from their presence.
Shadow searched for Rouge near the warehouse docks after her disappearance from GUN's contact. Informed Dr. Eggman's robots were hunting Mephiles down and mistook Shadow for him, the black hedgehog left to find the scientist for answers to Mephiles' identity. Upon meeting the doctor, Shadow learned a vital clue to Mephiles' possible origins that it pertained to the accident during the Solaris Project, and was offered more information on the project in exchange for capturing Mephiles. Shadow later thwarted Silver's second assassination attempt on Sonic and fought him to allow the blue hedgehog to continue his own mission. After fighting to a stalemate, Shadow managed to overpower Silver with Chaos Control until the latter hedgehog's own use of Chaos Control interfered with his, causing a portal through time to appear. Understanding that Silver had been trying to kill Sonic to prevent his apocalyptic future from occurring at Mephiles' suggestions, Shadow informed him that Mephiles was really using him to erase the past. Shadow then suggested that Silver accompany him to the past if they are to discover the truth of what happened ten years prior. Shadow then entered the area just as the accident occurred, and checked on the Duke's body, although he soon witnessed the birth of both Iblis and Mephiles. Shadow then pursued Mephiles, although not before being handed the Scepter of Darkness by the Duke to seal Mephiles, while Silver went after Iblis, rendezvousing briefly to get by a switch in their paths. Shadow then proceeded to use Chaos Control when cornering Mephiles, and then sealed him in the scepter, although not before the latter threatened that he will die in the future (explaining how he knew Shadow upon his release). He and Silver then returned to the future, leaving the scepter behind since he already knew its fate.
Meeting up with Rouge, Shadow requested her to contact GUN to see what the scepter was made out of, hoping to recreate it. He then rendezvoused with Omega upon learning that the latter had cornered Mephiles. By the time he and Rouge arrived, however, Shadow discovered that Omega had furiously driven Mephiles off. Omega then admitted that Shadow, in the future, is sealed away by the reprogrammed Omega. As the revelation shocked all of them, Rouge told Shadow that she would always remain by side even if the world would turn against him. Shadow's team then returned to Soleanna, where they had to find someone with archaeological knowledge on the object. They then rescued an archaeologist, who informed them that it would appear at a priest's fountain by lighting black flames, which Shadow accomplished. After taking out several of Iblis's and Mephiles' henchmen that had invaded the city from the desert, a grateful Lord Regis, acting under temporary authority after Eggman had kidnapped Elise a third time, opened the way to the desert. Deducing that Mephiles needed at least one Chaos Emerald to reform with Iblis into Solaris and devour time, the trio went to the ruins that Mephiles was headed to, most likely because a Chaos Emerald was nearby. However, they found Mephiles getting the Emerald in the ruins' inner sanctum. When asked once more to join, Shadow exposed what Mephiles' true plans were. After which, they then fought in an intense battle.
Although Shadow, Rouge and Omega ultimately won, Shadow's attempt to seal him failed due to Mephiles time traveling to his encapsulation and absorbing Shadow's power via his shadow, alongside his gaining of a Chaos Emerald (In the Japanese version, Mephiles said that since he had absorbed Shadow's power through the latter's shadow, Shadow cannot seal him again). Undeterred, Shadow, upon declaring to the newly created Mephiles clones that he will fight as he always had even if the world declares him to be as an enemy, and proceeded, alongside his teammates, to plow through the Mephiles clones with his full power backing him.
Despite seemingly wiping out the clones, Mephiles nonetheless gained ahold of the seven Chaos Emeralds (an event Shadow briefly witnessed immediately after slaughtering the clones when the yellow and green Chaos Emeralds glowed intensely) and merges with Iblis, becoming Solaris. Shadow, along with Silver, Tails, Knuckles, Amy, and Dr. Eggman, also discovered that Mephiles had killed Sonic to ensure Iblis' release (due to his sealing of Iblis inside of Elise weakening due to crying). In order to defeat Solaris before it consumed all of time, Shadow and the others proceeded to find the Chaos Emeralds to revive Sonic (Shadow finding one in Kingdom Valley). Afterwards, with Super Sonic's help, he turns into Super Shadow and joins him along with Super Silver to defeat Solaris.
After Elise extinguishes Solaris when it was just a tiny flame, the events of the game are then erased and do not occur; Shadow's future is then left open, since humanity would have yet to find reason to persecute him.
Shadow appears in Sonic Rivals as a playable character, alongside Sonic, Knuckles, Silver and Metal Sonic. Summoned to a strange island by Dr. Eggman via a cryptic transmission asking for his aid, Shadow is able to successfully locate Eggman and prevents Silver (who he meets for the first time due to their original meeting being retconned) from confronting him. Shadow assumes Silver was the one whom Eggman mentioned was targeting him, but once he mentions the cryptic message, Eggman denies it and sends his Egg Turtle on the hedgehogs. Initially deciding to leave things be, Shadow is contacted by Rouge who insists he keeps trailing Eggman while she uncovers more information. After contending with Knuckles in his pursuit of Eggman, Shadow is contacted by Rouge again only for the transmission to be cut short before she can reveal what she discovered about Eggman. Encountering Sonic and Metal Sonic, Shadow learns that Rouge had been captured within a card by Eggman and continues with more determination in learning what Eggman is hiding.
At one particular encounter, Shadow sees Eggman possesses a card of himself. Running into Silver again, Shadow is told that Eggman may really be an imposter, meaning the real Eggman has been trapped in a card. Finally confronting the villain, Shadow learns "Eggman" is really Eggman Nega, his descendant. After being bested once again, Eggman Nega plans to take a picture of the entire world, thus trapping it in a card, with his camera. The real Doctor Eggman is eventually rescued who escorts Shadow and Silver to Nega's space station to stop Nega's ultimatum. Assisted by Silver and Sonic in making his way through, Shadow is able to defeat Eggman Nega and Rouge is finally rescued. Shadow also appears on four of the 150 collectible cards in the game.
Shadow also appears in the sequel to Sonic Rivals, Sonic Rivals 2. He is confronted by Metal Sonic and Eggman via a speaker in Metal Sonic, and tells him that he needs help. Before he can ask questions, he and Metal Sonic find Espio and Silver. Curious as to why Silver has returned to the present, Shadow begins to follow Silver while Metal Sonic follows Espio. Eventually, Shadow forgets to ask the Doctor why he is helping him and just continues to work with Metal Sonic. Eggman then tells Shadow that Eggman Nega is trying to release the Ifrit with the seven Chaos Emeralds. He enters the Chaotic Inferno Zone to press a switch inside the dimension to seal the Ifrit in its own dimension and after engaging it in a battle, he and Metal Sonic proved to be victorious but they are trapped in the process. Metal Sonic tears himself open to reveal a Chaos Emerald, and Shadow uses Chaos Control to warp them back to their own dimension.
In Sonic Free Riders Shadow entered the World Grand Prix with Rouge the Bat as "Team Dark". While Rouge was only interested in the large cash prize and treasure that was given to the winners, Shadow's only interest was testing racing skills.
When the World Grand Prix started, Shadow and Rouge were fifteen minutes late to the opening ceremony. When they arrived, Omochao complained about their tardiness, but Shadow remarked that he had no interest in formalities. Discontent with the rule that three members were required for a team, but accepting it nonetheless, Team Dark chose their third teammate, an E-10000B, on a whim. At the races, Team Dark was insulted by their first opponent, Team Babylon. However, Shadow mocked his opponents in return as his team kept beating them.
After defeating Team Babylon, Shadow and his team faced Team Heroes. Though Sonic praised Shadow's earlier performance, Shadow replied that his opponents were no challenge for him. During their face-offs, E-10000B began to overheat, but Shadow showed the robot no sympathy. Insisting to continue the competition anyway, Shadow faced off against Sonic in a final race and won. Having beaten Team Heroes, Shadow told Sonic that he would never beat him.
In the finals, Team Dark faced Team Rose and was just one race away from winning when E-10000B began to smoke. However, Shadow kept pressuring the robot to continue. The two teams then quickly began arguing over how Shadow and Rouge treated their teammate. In the end, E-10000B was moved to the repairing department, while the rest of Team Dark had a final race with Team Rose by themselves. After beating Team Rose, Shadow and Rouge went for the Grand Prix Headquarters unannounced and took the cash prize and treasure themselves. As they were leaving though, Omochao informed them that they had only taken the dummy drops for the display and that the real prize was locked away, meaning they had to attend the award ceremony to get it.
Near the end of the World Grand Prix, Team Dark and the other teams came down with an equal amount of victories, and Shadow came to the award ceremony with the others to collect their prize. Once there, they were all told by Dr. Eggman (under his alias King Doc) that they had one more race against his Gear-jockey robots. Shadow and Sonic quickly saw through Eggman's ruse, but the doctor had them race anyway. After the race, however, Eggman revealed himself and announced that that he had been collecting all the data on the racers in the Grand Prix with his E-10000 to make the ultimate Extreme Gear that he could use for his own agenda and challenged them all to a race. After beating Eggman though, Shadow noticed that E-10000B was spewing out a lot of smoke. Metal Sonic then revealed himself as the one controlling E-10000B and passing fake data to Eggman, explaining for the doctor's loss.
Shadow and the others then watched as Metal Sonic challenged Sonic the Hedgehog to a race, which the robot lost. Afterwards, it was revealed that Eggman never had any prize to give to the winners of the World Grand Prix. However, Shadow remarked that it was nothing new to him, just like the doctor's other schemes.
In the Nintendo DS version of Sonic Colors, Shadow was at Asteroid Coaster seeking information when he found Sonic and Tails, and gave Sonic a mission to test out if Sonic was still capable of fighting Dr. Eggman. After the mission, Shadow declined any hint of concern for the duo, but Sonic took it as a compliment.
Reuniting with E-123 Omega, Shadow and his friend discovered secret amusement ride of Eggman's. On their way to investigate, they were joined by Sonic and Tails. They arrived at a lab where Tails discovered records of an experiment called Project "Mother" on the computers. Shadow was disappointed they did not find more to help, but Sonic just was just happy to find something and left. Omega then asked why Shadow gave Sonic information, to which Shadow said he was just happy to let Sonic do all the racing around. Omega found this hard to understand since Shadow and Sonic were equals, but Shadow just replied that data would not tell him everything, leaving the automaton stumped.
In the console/PC version of Sonic Generations, Shadow was sucked into White Space by the Time Eater. After completing all acts in the Dreamcast era, Shadow can be found in the City Escape hub. When found, he is waiting for Sonic, stating that he neither knows nor cares where they are, as long as he gets a chance to finish Sonic. He has a unique rival battle, where the two have to race each other on a looped pathway to and gain Power Cores to unleash special attacks. The battle is won when one depletes the other's ring count whilst using a special attack.
Shadow appears later on to motivate both Sonics, alongside Rouge and the all the other characters after their initial defeat against the Time Eater. After the Time Eater is defeated, Shadow shows up at Sonic's birthday party along with all the other characters. He is the only character who does not wave goodbye to Classic Sonic and Classic Tails in the end.
Several months prior to Sonic Forces, Shadow was on his way to Eggman's Facility to destroy the base. Along the way, he wiped out the Jackal Squad defense unit and easily defeated their captain, whom Shadow told to never show his face to him again, before heading in to destroy the facility.
A couple of months later, Shadow and his team went on a reconnaissance mission regarding a suspicious Eggman base. After being informed by Rouge that Omega went ahead of him, Shadow headed out to join up with him. After Omega, who attacked the base instead of investigating it stealthily, lost all communications with Rouge however, he went in search of the robot at his last recorded coordinates. There, Shadow met Infinite, a mysterious being who had just defeated Omega. As Infinite ridiculed Omega, Shadow demanded answers from the unfamiliar entity. It was then that Infinite revealed that he was the Jackal Squad's captain, and that his loss to Shadow drove him to get assimilated with Eggman's finalized Phantom Ruby prototype so he could never be as weak as he once was. Infinite then promptly repaid Shadow by trapping him in an illusion via the Phantom Ruby prototype's properties. Shadow ultimately escaped both the illusion and the doomed facility they were in, although not before learning that Infinite planned to overpower Sonic with his newfound abilities. About a month later, Shadow learned from Rouge that Sonic was in trouble, although he was seemingly unable to make it in time to help Sonic as he was overpowered by Infinite in the City and taken to the rebuilt Death Egg, leaving the world to assume him dead and lose hope of defeating Eggman quickly.
Shadow eventually discovered an imposter was wrecking havoc in his name. This imposter turned out to be a heartless and soulless replica created by Infinite, who served as a soldier in the Eggman Army, alongside replicas of Metal Sonic, Chaos and Zavok. This replica, along with the others and Infinite, allowed the Eggman Empire to conquer over 99% of the world. Six months later, when Sonic confronted the Shadow replica in Sunset Heights, Shadow destroyed his replica when it tried to attack Sonic, using his Chaos Control to freeze time right before the replica could strike and delivering a roundhouse kick to take it out in one hit. Linking up with the Resistance, Shadow revealed to them the true nature of Infinite's replicas and virtual reality powers, and joined the Resistance in the war against the Eggman Empire. He had Rouge collect intelligence regarding where they could locate Eggman's files on the Phantom Ruby and its power source, leading to Classic Sonic and Tails hitting the Chemical Plant for the data.
Eventually, Shadow took part in the final battle between the Resistance and the Eggman Army at the Eggman Empire Fortress, which the Resistance sought to break into in order to destroy the reactor powering the Phantom Rubies and win the war. Just as Shadow and the others got pushed back by Infinite however, Omega, fully operational again, came and distracted the villain. After that, Infinite put Eggman's endgame into effect: using his Phantom Ruby prototype, he created a virtual sun above the planet to drop on the Resistance with and kill them all. While Shadow awaited the outcome however, the sun was neutralized by the Avatar. Shadow then reengaged the Eggman Army while Sonic and the Avatar defeated Infinite and destroyed the Phantom Rubies' reactor. However, when Eggman entered the battlefield with a Death Egg Robot armed with the original Phantom Ruby, which was powered by the mech itself, the doctor began producing thousands of replicas that threatened to overwhelm Shadow and the Resistance. Fortunately, Shadow and the Resistance were saved when Sonic, Classic Sonic and the Avatar destroyed the Death Egg Robot, causing the Eggman Army's replicas to vanish and leaving the Resistance as the winners of the war.
In the aftermath, Shadow, alongside Sonic's other allies, bid farewell to Classic Sonic as he returned to his own world, and vowed to rebuild the world. Afterwards, back at the Resistance HQ, he watched the Avatar leave to go on their own adventure after the Resistance got disbanded.
In Team Sonic Racing, Shadow and his team joined Dodon Pa's Grand Prix alongside Dr. Eggman and his team. However, Team Dark's true intentions for joining the Grand Prix was to investigate Dr. Eggman. In that Grand Prix awaited opponents like Team Sonic, Team Rose and Team Vector. For the races, Shadow received the Dark Reaper to race in.
During a race between Team Dark and Team Sonic, Shadow focused solely on Sonic as they raced neck-to-neck in their speed-type racecars. Eventually however, Dr. Eggman intruded on the teams' race in order to compete against them on his own as a "special guest" (which Dodon Pa permitted despite knowing it was a lie). After Eggman began gaining the lead, Shadow, his team, and Team Sonic all agreed to put their feud aside and work together to keep Eggman from winning the race. Instructing his team to follow Team Sonic's example (only better), Shadow received a Slingshot speed boost from his team that allowed him to pass Eggman alongside Sonic. Shadow and Sonic would afterward pass the finish line while the others took care of Eggman with a combined Wisp power-up assault. However, Dodon Pa was too busy watching Eggman's beating to see which one between Sonic and Shadow crossed the finish line first. As such, the two hedgehog decided to have a rematch.
Eventually, Shadow met Sonic after a race, who wanted to know if he was working with Dr. Eggman. Shadow replied grimly that he was only in the Grand Prix to stop whatever evil plans Eggman was cooking up. However, the two hedgehogs' egos soon clashed, and Shadow and Sonic ended up challenging each other to a race. Afterward, they agreed that they had to watch out for both Dodon Pa, whose motivations for hosting the Grand Prix was a mystery, and Eggman. Soon after, Shadow learned that Eggman and Dodon Pa were seemingly working together. Since they did not know what the pair was up to though, the heroes decided to keep racing for now. Later, Eggman would sent hundreds of Eggpawns after the racers. As Shadow set out to slag the robots with his team, he would end up competing with Sonic over who could beat the most Eggpawns. Later, after it was revealed that Dodon Pa was a good guy and that he was using the Grand Prix to gather information for his corporation's Ultimate Energy Engine, which Dodon Pa wanted to use for philanthropic purposes, Shadow came to Sonic and reminded him that they still had Eggman to worry about.
Soon after, the heroes learned from Big that Eggman had kidnapped Dodon Pa and brought him to the Final Fortress. Wanting to rescue Dodon Pa, Shadow and co. went to the Final Fortress. There, Eggman had them compete in a number of races with Team Eggman and his army of Eggpawns in exchange for Dodon Pa, not knowing Eggman was using them to gather the Ultimate Team Energy needed to finish the Ultimate Energy Engine. Once the engine was complete, Eggman stole it from Dodon Pa and incorporated it into his Death Egg. Shadow and his crew subsequently faced the Death Egg, and beat it in a race. However, the Death Egg soon after went crazy and drove into the Final Fortress's core. As the Final Fortress crashed, Shadow and his comrades were forced to abandon their cars and evacuate the airship while Team Sonic saved Dodon Pa. Down on the ground, Shadow was reunited with Team Sonic when they arrived with Dodon Pa. Just as the Grand Prix seemed over since the cars had been destroyed when the Final Fortress crashed, Dodon Pa decided to give everyone new cars, thus allowing Shadow and his allies to race once more.
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