How do you use chaos spear on shadow the hedgehog?

To perform the chaos spear move, Shadow must be in his super form- accessible in the last boss battle against Devil Doom. Hold down the attack button (the one that you would use to fire a weapon) and wait until a blue light surround Super Shadow. Then, release the button. He will fire a lightning bolt of blue energy toward the target and he may say 'Chaos spear!'.