As if the attacking doors weren't enough...
This battle must be won quickly, as the Demon Wall will constantly close in on the party, and when it gets close enough, will start to use an Instant Death attack called Crush.
This battle is difficult, as the Demon Wall has 99,999 HP. Giving Rosa the Dualcast augment before the battle makes it slightly easier. Rydia should always use her best summons, and Kain, Cecil, and Edge always attack on their turns. When it is Rosa's turn, she should Dualcast Slow on the Demon Wall and Haste on herself, then cast Haste on everyone else. Afterward, Rosa should cast Berserk on Cecil, Kain and Edge. Rydia should keep summoning.
Killing Demon Wall rewards an abnormally high amount of EXP points, which can help prepare for the end game.
demon is "an evil spirit or devil, especially one thought to possess a person or act as a tormentor in hell."A