Hidden Characters
To unlock all the cheats and hidden items in the game, go to the question mark at the bottom right of the Krypt wall and click it. You then input the necessary code to unlock what you are looking for. Four hidden characters are available in total. To unlock Meat, press "Up," "Square," "Square," "Circle," "Circle" and "Up"; for Blaze, press "Triangle," "Square," "Left," "L2," "Left" and "Circle"; for Taven, press "L2," "Left," "R2," "Up," "Circle" and "Down"; and to get Daegon, press "R2," "L2," "Triangle," "Down," "Down" and "Square."
Hidden Arenas
The game has four hidden arenas. To unlock the Nethership Interior, press "R2," "Left," "Left," "Down," "L2" and "Square"; to get the Pyramid of Argus, press "R2," "L2," "Square," "X," "R2" and "Up"; for Shinnok's Spire, press "Left," "Left," "Circle," "Up," "Triangle" and "L2"; and to get the Krimson Forest, press "Circle," "L2," "Up," "Square," "Circle" and "Down."
Music and Art
To get the Armory Fight theme, press "X," "Square," "Left," "Triangle," "Square" and "X." You can also unlock a piece of art from the game designers called "The Pyramid at the Crack of Dawn." To obtain this, press "Triangle," "Left," "Left," "X," "Down" and "Circle."
Chain of Fatalities
You can chain together as many as 10 fatalities at the end of the battle for the highest level -- an extreme fatality. You can perform a fatality starter, such as an arm break or a head kick, only once, but you can chain these together. When you get near the end, do a transition fatality such as drawing your sword. Defeat your opponent with a finisher, such as a head rip, to complete your fatality chain.