Shadow is depicted as having amnesia in his game, but in other entries is shown as more dark to Sonic’s light, a sometimes-rival to the Blue Blur with an anti-hero vibe.
Shadow had a caring, protective bond with Maria, who was killed right before his eyes when GUN deemed Shadow too dangerous and captured him, throwing him in stasis until the modern-day Dr. Created by Robotnik’s grandfather, Gerald, 50 years ago when he tried to make “the ultimate life form” to master the chaos emeralds, Shadow was part of Gerald’s plan to cure his granddaughter, Maria Robotnik, of her terminal illness. We know Shadow, of course, from 2005’s eponymous Shadow the Hedgehog.