Collecting Fire Souls will unlock another difficulty for the Computer players and other extras in Party Mode.

Effect - Code

Aim! Big Crossbow: 6 Fire Souls
Cross! Balance Race: 48 Fire Souls
Extreme Difficulty: 114 Fire Souls
Final X Adventure: 126 Fire Souls
Fly! Ptero-Rider: 78 Fire Souls
Play as Blaze: 105 Fire Souls
Play as Cream: 42 Fire Souls
Play as Shadow: 30 Fire Souls
Play as Silver: 87 Fire Souls
Put It Out! Big Fire: 60 Fire Souls
Reel! Battle Fishing: 24 Fire Souls
Row! Canoe Race: 18 Fire Souls
Sink 'Em! Pirate Ship: 12 Fire Souls
Spin! Propeller Race: 96 Fire Souls
Thrust! Bone Knight: 36 Fire Souls
Watch Out! Trap: 54 Fire Souls
World Bazaar: 69 Fire Souls