Free all the Mul-muls from their cages, and they will unlock special Runes in each level. You can check how many Mul-Muls you’ve freed in the Extras Menu.
Developer Upgrades
Be sure to collect all of your special upgrades to help your Heroes through their journey (keep your eyes open for the sparkling light). To view all of the Skills that you have unlocked, enter the Extras Menu.
Invincibility
Press Start to pause game play, then press L2, L1, Circle(2), Square, R1(2), R2.
Unlimited health
Press Start to pause game play, then hold L2 + R2 and press Square(2), Triangle, Circle, X(2).