During a game, hold L1 + R1 + Triangle + Square + Circle + X and press Start.

Level 10 Character

During a game, hold L1 + R1 + Triangle + Square + Circle + X and press L2.

Extreme Mode

Beat the game on any Difficulty setting.

Play as Atermis Entreri

Beat the game on Extreme Difficulty.  Then, while at the Character Selection screen, highlight Alessia Faithhammer and press Down, Down.

Play as Drizzt Do'Urden

Beat the game on any difficulty.  Then, while at the Character Selection screen, highlight Alessia Faithhammer and press Down.