The twelfth experiment to create a life form to specifically kill Shadow the Hedgehog.
Spine was created to kill Shadow the Hedgehog, he went rogue and became a mercenary. He was hired by Dr. Eggman to defeat Sonic, but unfortunately he caught a glance of Shadow the Hedgehog during the fight. Spine reflexively attacked Shadow. After he was subdued he was put into a holding cell. He escaped and then went into hiding.
1 year later, Spine discovered a long lost facility called subject 12 bay 6. Inside were thousands of clones of Spine. After he accidentally activated them they all attacked him, mistaking him for Shadow the Hedgehog. Spine managed to rig the bay's generator to explode, escaping just in time. After the clones were dead, Spine discovered that there were 5 other bays filled with imperfect clones of himself. He set out to destroy the other facilities.