Unlocking the extra characters

Unlockable              How to Unlock
Blade                   Complete the game once on any setting.
Classic Ghost Rider     Complete the game once on any setting.
Vengeance               Get every skull in Story and Challenge Mode.
Ghost Rider 2099        Clear every level in Story and Challenge Mode 
                        on the "punishing " difficulty.

Cheat List
     To  be  able to reach the list of the available cheating you have
to  end the game at least in normal mode. Then they will be accessible
from the menu extras.

Unlockable              How to Unlock
Invincibility           End the game in normal difficulty
First mortal blow       End the game in normal difficulty
Charge link infinite    End the game in normal difficulty
Infinite spirit         End the game in normal difficulty
Mode turbo              End the game in normal difficulty