In the long corridors of the Death Egg, Dr. Ivo Robotnik Has just completed his greatest creation yet, Project: Metalix, 6 months later, a green hedgehog named Ashura locates "Eggman's" base and plans to sabotage the robot, what could possibly go wrong?
The two mission characters that follow you and give you hints are: Hero char. is Sonic and Shadow, Dark char. is Metal Sonic and Dr. Eggman
Much like Shadow, Ashura will use any means necessary to get his way, including, sometimes, stealing G.U.N.'s weapons and using them against them, but you can also find special Gauntlets that eiher shoot out Chaos Spears, or project out a Chaos Force shield
The main hero mode bosses instead of Black Doom and Black Bull are the groups of Mecha Sonic's sent by Metalix or Eggman, the Main dark mode bosses instead of Sonic and Diablon are shadow's G.U.N. troops and Machines
When the humans or Sonic and Co. see you as some sort of threat, they would send in reinforcements to stop you, they would include Metal Sonic telling you to kill all the Soldiers and Sonic and Co. telling you to destroy all of the Silver Sonic's sent by Eggman
With a full Hero Gauge, Ashura can unlock his hidden power of Chaos Control, but with a full Dark Gauge Ashura can unleash the power of Chaos Force by launching a huge green blast at enemies as a kick, his homing attack colour is red, like Shadow's is orange and Sonic's is blue, Ashura's Melee isn't that good but his Gauntlets make up for it
In Knuckles, Super Knuckles defeated Perfect Chaos But here Ashura Learns that Metalix is Evil and wants to rule the world with an Imperial army of Robots, so using the Chaos Emeralds he's Collected he turns into Super Ashura and flies off after him, but it's already to late Metal Sonic transcends his Metal Overlord state and flies off into space, Ashura already there, encases the Planet with a Chaos Force Shield and goes out to Face down Metalix.