Sonic Adventure 2
Shadow debuted in the game Sonic Adventure 2 as one of three main antagonists, alongside Rouge the Bat. Dr. Eggman set Shadow free from a G.U.N. base on Prison Island, where he had spent 50 years imprisoned. In exchange, Shadow agreed to aid the doctor in his plans to take over the world; holding in secret his true intentions as wishing to get revenge for the death of his friend, Maria Robotnik. To achieve this, Shadow revealed the primary weapon of the Space Colony ARK - the Eclipse Cannon - to Dr. Eggman, blowing up half of the Moon in demonstration. In a twist of fate, Shadow ultimately aided Sonic when realizing Maria's true wish with the help of Amy Rose (Chris in the anime "Sonic X"), which was to save humanity.

In the Last Story, Eggman inserts the final Chaos Emerald into the Eclipse Cannon's power core, only to initiate a destabilization program on the ARK. Gerald Robotnik then revealed that he had made this function to have revenge for Maria, and that the ARK would destroy the Earth. Meanwhile, Sonic and Knuckles had reached the Central Core, where they ran afoul of the Biolizard, the Prototype of the Ultimate Life Form (and technically Shadow's older brother). After Shadow arrives to distract (and ultimately defeat) the Biolizard so Sonic and Knuckles can deactivate the Emeralds, Knuckles uses the Master Emerald to stop the Chaos Emeralds. But the Biolizard uses Chaos Control to fuse with the ARK and create The FinalHazard, continuing the station's plummet toward Earth. Then, as Super Sonic and Super Shadow, they destroy the FinalHazard, and using their pooled energies, use Chaos Control to move the ARK safely back into Earth's orbit. Afterwards, Shadow fell to the earth and was presumed dead.

Sonic Heroes
In Sonic Heroes, Rouge discovers Shadow in a stasis tube located in the deepest part of one of Dr. Eggman's bases. As she activates the capsule, E-123 Omega begins to attack the newly awakened Shadow, believing him to be an android. Shadow discovers that he has amnesia and cannot remember anything before his release. He joins forces with Rouge and the robot E-123 Omega to form Team Dark and find Eggman, who mockingly announces that he has no past to remember. At one stage Shadow even finds a robot version of himself in pieces. Rouge later discovers an hangar filled with hundreds of Shadows in capsules similar to the one in which she found him. Omega implies that cloning is involved, and that the original must exist for the clones to have been made. It is later revealed that Eggman had made robotic android versions of Shadow, and the question is raised as to whether or not Shadow himself is one of these androids. Ultimately, when Metal Sonic transforms into Metal Madness, Shadow works with everyone else to help defeat it. Shadow is last seen with Omega and the defeated Metal Sonic.

Sonic Battle
In Sonic Battle, Rouge 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 one of Gerald Robotnik's journal entries, he mentions that "Project Shadow" was put on hold because of Project Gizoid.

Shadow the hedgehog
In Shadow the Hedgehog, Shadow is revealed to be the dual creation of the alien overlord Black Doom and Professor Gerald. Gerald could not finish the project on his own, so he contacted the Black Comet and used Black Doom's blood, and presumably his DNA to create Shadow. Shadow eventually gathers all the Chaos Emeralds and confronts Doom as Super Shadow. He then destroys the Black Comet with the Eclipse Cannon. In the end, he puts the past behind him. Also in the last battle of the game, Eggman confesses to Shadow that he saved him in Sonic Adventure 2 before he fell to Earth, meaning he is the real Shadow and not a Shadow Android as was previously believed.

Sonic the hedgehog (06)
In the 2006 Sonic the Hedgehog game, Shadow is a playable character and has his own storyline which weaves with those of Sonic and new character Silver the Hedgehog. In this role, Shadow encounters the new villain Mephiles the Dark when the Scepter of Darkness falls and shatters. Shadow is sent to the future and is revealed to have become the enemy of mankind, due to their fear of his power. It is also been revealed that Shadow is sealed away by the reprogrammed Omega sometime during this event. Eventually, Mephiles gains hold of the seven Chaos Emeralds and merges with Iblis, becoming Solaris. Shadow turns into Super Shadow and joins with Super Silver and Super Sonic to defeat Solaris. The events of the game are then reset and do not occur, possibly leaving his future open.