Disgaea 2 Dark Hero Days(How to level up faster to level 500)

You need to open up Cave Of Ordeals First.Any characrters with at least 700 mana can unlock Cave Of Ordeals in the Dark court.To unlock the Land of Carnage (a mirror world of every level with super difficult enemies), collect all 16 treasure maps from the different pirates in the Item World.And the last one that you must have is....One powerful characters to make it happens.