In Sonic the Hedgehog 3, it's revealed that Shadow was discovered after crash landing on Earth in a meteorite 50 years ago. The government sets out to harness his Chaos Energy and, during his captivity, Shadow befriends Maria, Dr. Gerald Robotnik's granddaughter.
She dies when a G.U.N. soldier inadvertently causes an explosion during Gerald, Shadow, and Maria's attempted escape. In the present day, Shadow teams with Gerald and Doctor Eggman to take revenge, putting the entire planet at risk when they steal the Eclipse Cannon.
Enraged after Shadow injures Tom, Sonic goes into "Super Sonic" mode by using the Master Emerald to defeat the anti-hero. Realising his desire for revenge makes him no better than Shadow, Sonic shows mercy and convinces his foe that Maria wouldn't want any of this. The two form an alliance - both going "Super" - and bring down Gerald's space station after he reveals his plan to wipe out all life.
He's disintegrated by Chaos Energy, Knuckles and Tails save Sonic, and after stopping Earth's destruction, Shadow seemingly dies in an explosion (alongside Eggman who goes out a hero after helping stop his grandfather destroy the planet; it turns out that not even he wants to kill everyone).
Life returns to normal for Sonic the Hedgehog 3's heroes and they resume the race they were going to have before Shadow showed up.
The mid-credits scene reveals that Sonic won the race; however, he's gone too far and ended up in a forest on the outskirts of New York. The speedster is ambushed by a group of Metal Sonics and is saved by a hammer-wielding hooded figure.
She's revealed to be Amy Rose, Sonic's love interest in the games and a major new addition to this franchise. As you may recall, both Metal Sonic and Amy were introduced in Sonic CD, so it appears a possible fourth movie will delve into time travel and Eggman ruling over a future Earth.
In the second stinger, we find a crater with one of Shadow's inhibitor rings; however, by taking on his "Super" form in Sonic the Hedgehog 3's closing moments, he survived that explosion and his feet are shown walking into the shot as the screen cuts to black. Shadow lives!
Sonic the Hedgehog returns to the big screen this holiday season in his most thrilling adventure yet.
Sonic, Knuckles, and Tails reunite against a powerful new adversary, Shadow, a mysterious villain with powers unlike anything they have faced before. With their abilities outmatched in every way, Team Sonic must seek out an unlikely alliance in hopes of stopping Shadow and protecting the planet.
Director Jeff Fowler returns along with our all-star cast including Jim Carrey, Ben Schwartz, James Marsden, Tika Sumpter, Idris Elba, Colleen O'Shaughnessey, Natasha Rothwell, Shemar Moore, Adam Pally, Lee Majdoub, newcomers Alyla Browne and Krysten Ritter, with Keanu Reeves joining the franchise as Shadow the Hedgehog.
The story was written by Pat Casey & Josh Miller; they also penned the screenplay alongside John Whittington.
Sonic the Hedgehog 3 is now playing in theaters.