> Pause the game, hold the L and R triggers, and enter a code:

Aerial Reaver -- A, Right, Up (x2), Y, Left (x2), Right, Up. 
All abilities -- Up (x2), Down, Right (x2), Left, B, Right, Left, Down. 
Fire Reaver -- Down, Up, Right, Up, Down, Left, B, Right, Down. 
Force Glyph -- Down, Left, Y, Down, Up. 
Kain Reaver -- A, B, Right, Y, Left (x2), Right, Up. 
Maximum health upgrade -- Right, B, Down, Up, Down, Up. 
Maximum magic upgrade -- Y, Right, Down, Right, Up, Y, Left. 
Open all warp gates -- Up (x2), Down, Right (x2), Left, B, Right, Left, Down. 
Restore health -- Down, B, Up, Left, Up, Left. 
Restore magic -- Right (x2), left, Y, Right, Down. 
Sound Glyph -- Right (x2), Down, B, Up (x2), Down. 
Stone Glyph -- Down, B, Up, Left, Down, Right (x2). 
Sunlight Glyph -- Left, B, Left, Right (x2), Up (x2), Left. 
Upgrade health to next level -- Right, A, Left, Y, Up, Down. 
Water Glyph -- Down, B, Up, Down, Right.
(courtesy: GameFan)