Mace:The Dark Age
Level Select
To select a particular stage in which to fight, go to the character's portrait in player select and tap START four times. Then select your character as usual.

Play As Grendal in One-Player Mode
To play as Grendal in 1 player mode you have to beat everyone up to the Executioner and let him kill you. Then highlight the Executioner and push Start + Evade to get Grendal, then press any Attack button to select him.
 Level Select
 Play As Grendal(1p)
 Play As Grendal(2p)
 Play As Ichiro & Gar
 Play As Janitor
 Play As Pojo
 Secret Battles
Play As Grendal in Two-Player Mode
Starting in two-player mode, one player must have three wins. Then on your next match in the select screen go to the Executioner and hold down START and EVADE. Grendal will appear. Continue to hold down those buttons and press an attack button to select. Now you control the RAGE known as Grendal!

Play As Ichiro and Gar
To access Gar Gunderson (War Mech) and Ichiro in Mace wait for the copyright screen to load up (the first screen in the game) and press Right, Up, Left, Down, Right, Up, Left, Down on your controller pad. In other words, rotate the control pad in a counter-clockwise direction. If you've done everything right you'll hear a chime. Now go to the character selection screen and Ichiro and Gar Gunderson will be selectable just above the Executioner.

Play As Janitor
At the character select screen, move the cursor to the following fighters and press START on each one: Koyasha, Executioner, Lord Deimos, Xiao Long. Now pick any fighter and press A or B.

Play As Pojo
To be POJO, you must perform TARIA's execution in one-player mode (and then continuing) or in two-player mode. Then on your next match in the select screen, go to Taria and hold down START and EVADE. POJO will appear - press an attack button to select. Pojo will now unleash her awesome fighting prowess for you.
To select Pojo, press any attack button. To change her color first, hold START then press one of the C buttons or EVADE. To make Pojo throw an egg, jump and press Strong + Quick.

Secret Battles
To unlock each secret, move to each character listed and tap start after each one, then go to your desired character and select as usual. All of these secrets are for two-player mode except for the Random AI.

 
Battle           Characters
Castle           Mordus Kull, Taria, Ragnar
Big Noggin       Ragnar, Al' Rashid, Takeshi
Random AI        Hell Knight, Xiao Long, Dregan, Namira
Miniature Golf   Koyasha, Mordos Kull, Takeshi
Credit Goes To: IGN 64