You appear in the Mushroom kingdom and see Devil Mario (a Mario who was possessed by many Boos) massacring the Toads and Yoshis who try to stop him from obtaining the Power Stars to destroy all of existence. Seeing you on his way, this Mario runs against you to attack you too but stops when a sinister voice is heard while an evil presence teleports away, showing himself as Sonic.exe

[Sonic.exe] "Hello... Do you want to play with me"

Devil Mario with a blow knocks Sonic.exe back, Sonic.exe smiles sinisterly, Devil Mario ignores you, and now looks angrily at Sonic.exe

[Devil Mario] "Who are you?"

[Sonic.exe] "I... am... Death!

Devil Mario decapitates Sonic.exe with a single blow and then walks away indifferently but Sonic.exe regenerates and grabs Devil Mario's foot and throws him to the ground. Devil Mario is surprised but seriously catches and hits Sonic.exe quickly, Sonic.exe with his abilities teleports and attacks Devil Mario with a Spin Dash. Devil Mario falls to the ground but with his great speed, strength and fighting style he manages to reach him and grab Sonic.exe by the neck, hitting him several times, but Sonic.exe teleports them to another place dodging

Sonic.exe with a sinister smile strategically teleports around Devil Mario, but Devil Mario manages to predict it easily. Sonic.exe snaps his fingers and makes his reanimated victims appear to attack Devil Mario, Devil Mario manages to kill everyone, but when he is distracted Sonic.exe grabs him by the neck and opening his mouth was going to absorb his soul but instead he absorbs some Boos from Devil Mario's body, Devil Mario manages to escape in time, somewhat weakened by the loss of some Boos. Devil Mario, to compensate for the loss, absorbs one of the Power Stars and covers himself with a red aura. Sonic.exe absorbs the Boos (since they are souls) transforming into Dark Sonic.exe

[Sonic.exe] "So many souls to play. You'll die in my hands"

[Devil Mario] "You fall in my hands"

Devil Mario and Sonic.exe start exchanging blows