Eternal Darkness: Sanity's Requiem Cheats for GameCube
Unlock Level Select:
The 'Jump To Game' option is unlocked when you complete the game twice using the same game 'Save' file (you have to choose a different artifact in Roman Dude's stage).
Complete the game 3 times using the same game 'Save' file to unlock Eternal mode under the 'Jump To Game' option.
Use the Reveal Invisible spell with the Mantorok to make your character invisible.