A firearm and a branching conscience define Shadow the Hedgehog. Sega gave the black hedgehog guns and a hero-or-villain story in 2005, with Black Doom's alien army as the invasion that forces the choice.
Chaos Emeralds, a dark mission, and a hero mission can split the same level into different endings. Vehicles and a weapon wheel sit beside the usual homing attack, which is why fans of the speed alone often bounced off the combat.
Sonic's team games had kept Shadow as a rival in someone else's plot. This one hands him the guns, the aliens, and a last decision about which side the black hedgehog takes.