arc in this show  (comprising "Blackbot the Pirate", "Hedgehog of the Hound Table",  "Robotniks Pyramid Scheme" and "Prehistoric Sonic"), there are four  Chaos Emeralds, all of which are green and of various shapes,  scattered throughout various points in history, and each give a  specific power: invisibility, invincibility, immortality and the  power to give life.