One way to help take enemies down in droves is to grab an enemy, and effectively use them as a weapon, to bat around other incoming enemies. Not only do you gain a longer range weapon as a result, but it hurts both enemies when hit.
To get the alternate costume for a character, highlight that character and press [R1].
When the loading screen with the skull appears, use the Left Analog-stick to move the skull. Use the Right Analog-stick to move the word "Loading".
21's Arena(Prisons of Akrowla)-Run through the door and around the corner, then break the doorway to drop into the lower sectors of Akrowla. Smash the fllen cages to reach the lava area.
Dagan's Arena(Lost Fortress of Skurlock)-Smash through the wall to the east and jump down to the second level. Continue moving east and use a jump atack to break through the brige to another hidden zone.
Eyaa's Arena(Venomous Swamp)-Run Behind the Waterfall
Jin's Arena(Lower Darklands)-Break thru the ledge to the southeast t reach the entrance to the second level. Next run thru the doorway to the North to gain access to the third floor
Keela's Arena(Shorestone Castle)-Break the South Tower Wall and fall to the shore
Malik's Arena(Land of Desolation)-Break the scaffolding to the right, then plummet to the second level. To reach the next area, you'll need to knock the opposition through the temple archway
Mongo's Arena(The Forgotten Ruins)-Smash through the rock blocking the door in the far corner of the arena. Then run thru the planks to another hidden section.
Stitch's Arena(Underground Sewer)-Break through the wal in front of the pit,ttt ttttttthen jump in.