Disgaea: Hour of Darkness
The Item World is a world where the player can send the characters into an item. The levels in the Item World are randomly made, and at every ten floors, there's a more powerful enemy and an exit. The more floors the player goes to, the stronger the item gets. In Item World, there are also characters called Specialists. If one of the player's characters kills them, they are captured, and make the item more powerful in some ways. For example, if the player captures a Gladiator, the item boosts the attack power of who's holding it.