Every single item in the Disgaea universe has a random dungeon inside of it, which extends to this game. You will unlock the Item World near the end of Episode 3 and will actually be required to level a given item in order to progress through the story. Unlike previous games, the rarity doesn’t affect how many floors an item has, so you can continually go through floors, as they are now infinite. However, there is an initial cap on an Item Level in this game, which is set at 500. Once you clear all of the Quests that involve the Carnage Dimension, you will be able to pass a bill in the Item Assembly to increase this cap by another 500, and do this until you reach the ultimate cap of level 9999.
The Item World functions a little differently than in previous entries, as you can no longer level the item by just reaching the portal on each floor. The Bonus Gauge on every floor has an "item level" reward for ranks 1 and 9. If you exit a floor by using the portal, then the rank 1 reward will disappear (you get to keep any other items you got on the Bonus Gauge, though). To compensate for this, the normal enemies you encounter on every floor are weaker than enemies found elsewhere. All other enemies in the Item World will have normal stats (bosses, Netherworld invaders, etc).
There is no limit to the number of floors you can explore, as it will keep going on and on. The enemies only ever grow stronger as you actually level the item you’re currently in, so if you keep skipping floors without defeating all of the enemies, then they will remain around the same level as when you entered. This is an extremely useful tip when you’re farming for Innocents, as this will keep them at a low enough level for easy subduing.
Item World NPCs
You’ll be encountering plenty of other things in the Item World than just enemies. Sometimes, you’ll see little rabbit creatures holding signs. These are called Lucky Boards and depending on the sign they are holding, they will grant various bonuses related to that board (ex. a coin means that you’ll gain extra HL from killing the Lucky Board). It should be noted that Lucky Boards have an Evility that basically cancels all damage that isn’t greater than their max HP.
Another NPC you’ll come across as you venture through items is a bottle, which is called a Bottlemail. These things are usually a higher level than the enemies you are currently fighting, as well as having a lot of defense. Unlike Lucky Boards, you can whittle their HP down little by little until they are defeated, as you don’t have to worry about one-shotting them to do damage. Your reward from Bottlemails usually include a scroll of some kind, either in the form of a skill or an Evility.
The above two NPCs don’t usually appear on their own, as there is a special NPC that has a chance to spawn them at the beginning of each floor (except for the multiples of 10). This NPC is called Mr. Egg and will randomly show up from time to time, dropping either a Bottlemail or Lucky Board. However, there is one more thing Mr. Egg can drop, which is a very powerful enemy named Proto Darkdeath. This enemy will be a much higher level than you and with much higher stats, so you’ll need to be careful. Note that killing him will boost your item’s stats by a bit.
Item Stats and Bosses
On every floor that is a multiple of 10, you will encounter an Item Boss. On floors ending in 10, 20, 40, 50, 70 and 80, it will be an Item General. For floors ending in 30, 60 and 90, it will be an Item King, while floors 100 will have an Item God. The first benefit that killing these Item Bosses will have is an increase in stats. Unlike previous games, using a Gency to exit the item after killing one and killing the boss again has no benefit, so there’s no reason to do this.
One stat that is present on every single item is something called Rarity, which can range from 0 to 100 (store bought items are always 0). Any Disgaea veteran will know about Common (0-24), Rare (25-49) and Legendary (50-99) items, which is nothing more than the Rarity being in a specific range. There is a new Rarity introduced in Disgaea 5, though, called Epic (100), which is only achievable by diving into the Item World.
Rarity will increase the stats of an item according to the number itself, so a Rarity of 50 will increase the stats by 50%. Matching Rarity is still in the game, meaning that if you have equipment that has the same kind of Rarity (Rare and higher), then you will get a stat bonus on them. Two matching items will grant a 10% increase and four items will grant a 30% increase. The numbers don’t matter, as only the general Rarity does.
How does one raise Rarity? Raising the Rarity number is tied to something called the Training Bonus, which can be raised in a few ways. The simplest method involves simply killing the Item Bosses, with Generals providing a bonus of 1, Kings a bonus of 2 and Gods a bonus of 3 (Proto Darkdeath functions the same as an Item God in this case). You can also raise the Training Bonus by defeating all of the Invaders that can appear on any given floor. Also, you’ll sometimes get into fights in a Mystery Room and if you win the fight, the Training Bonus will increase.