Disgaea 4: A Promise Unforgotten Power Level Maps. It is highly recommended that you have multiple allies in Evil Symbols: like Aura Pyramid or Training Ground to leech the extra mana or exp from. You can also expand your Evil Symbol by visiting the Chara World.
Map 1-1(Episode 1: Rebels of Hades - Rehabilitation Room[]
This Map has a EXP+50% effect along with a Mana+50% effect. There are 2 Prinnies on the EXP+50% effect and 2 more Prinnies on the Mana+50% effect. This is a good stage to level up your characters before 1-3 or 1-4.
Map 1-3(Episode 1: Rebels of Hades - Prinselytise Room[]
There are 3 EXP+50% Geo Blocks which can be thrown on the DEF+50% panels. After throwing 1 or 2 EXP+50% Geo Blocks onto the DEF+50%, finish off all of the enemies.
Map 1-4(Episode 1: Rebels of Hades - Albatross Collar)[]
Throw the red Geo Block towards the blue panels then destroy the red Geo Block to create a massive geo chain. Finish the remaining enemies.
Map 2-2(Episode 2: Prinny Wars - Hypha Invasion)[]
Throw the blue Geo Block towards the green panels then destroy the blue Geo Block to create a massive geo chain. The power leveling trick works vice-versa as well. You can also throw the green Geo Block towards the blue panels then destroy the green Geo Block to create a massive geo chain.
Map 2-6(Episode 2: Prinny Wars - Altar of Waste)[]
In this stage you fight a bunch of slime units. Take advantage of their low range and elemental weakness to fire by using a long range attack or a fire spell. After you killed a majority of the enemies, kill either Geo Block to improve your bonus rank. To prevent damage from the geo chain, stand on your base panel and use an area of effect spell. Although this is not necessary due to Geo Chains dealing minimal damage.
Map 3-2(Episode 3: Enter the Final Weapon - Searing Euthanasia)[]
This stage is good for gaining Mana, EXP or HL due the the EXP+50%, Mana+50% and HL+50% Geo Effects. The groups of enemies below can easily be wiped out with an area of effect attack. The Mothmen on the EXP+50% can be combined to make a more powerful enemy that easily gives lots of EXP.
Map 5-2(Episode 5: The Angel of Avarice - Lost Dignity)[]
Get a unit close to the yellow geo block by either throwing or using a character with high Move. Afterwards, throw the yellow Geo Block towards the purple panel then destroy it to activate the 150% exp bonus panel. Use high area of effect spells to clear the mobs of enemies. Majority of enemies are weak against ice except the alraune. Pass several stronger enemy bills to gain additional experience.
Note that by passing exactly 8 Stronger Enemies bills, the enemies of this map will all be level 99 and, due to the way Exp is calculated, they will actualy give as much Exp as level 323 enemies.
Map 5-4(Episode 5: The Angel of Avarice - Ruin Coaster)[]
The Level 99 EXP trick can easily be used here. There are 2 groups of 3 Level 33 Bouncers near the Base Panel. They can be combined (by throwing them together) to form a level 99 enemy that gives out as much EXP as a level 323. Pass Economic Stimulus Act for triple EXP. By killing the first level 99 enemy, a character can easily gain 15+ levels with the bill passed. There are 2 more groups of 3 Level 33 Bouncers near the end of the map.
Map 8-7(Episode 8: Battle! Final Boss vs. Final Boss - Mission Improbable)[]
Although the Level 99 EXP trick cannot be used here, this is a good map to level on as the enemies are forced to walk to you single-file across Silence and HP/SP switch Geo Blocks. This is an ideal map to grind up levels for any humanoid units that use Bows, Guns, or Magic.
Map 9-4(Episode 9: The Moon, Earth, and the Promise! - Concrete Knowledge)[]
This is the second best grinding map in the entire game.
Throw the blue Geo Block vertically towards the aqua panel to get an additional EXP +50% bonus. ***Optional: throw the purple Geo block vertically towards the aqua panel to get addtional Mana +50%. This is not recommended due to the extra time it will take..**** Bring Desco out then fuse her with another monster unit so she will gain extra special attack range. Use the Yog Sothoth special attack to finish the enemies. Desco learns Yog Sothoth at level 100. If Desco is too weak, use beast tamers, brave heart or equip and unequip a weight to activate her 3 Transformations evility. Pass one stronger enemy bill to make the enemies level 99 so you can exploit the experience system. Fuka and Valvatorez can each use their ultimate skills to kill one row each.
Also, include either a Bouncer or Fenrich in the Training Ground Evil Symbol to leech some exp to learn the tier 6 fist attack Big Bang, so you can prepare for the best grinding spot, Training: Mt. Ordeal 4. Bouncers learn Big Bang at Tier 4. Fenrich learns Big Bang at level 500.
Map Training Mt. Ordeal 4[]
This is the best grinding map for exp or mana in the entire game.
Place a Nekomata in the Fusion Weapon Lab evil symbol. Go to Mt Ordeal 4 and fuse a monster with Nekomata then magichange a unit with the Big Bang weapon skill. Use the upgraded Big Bang skill to kill all the enemies in one hit. You can learn Big Bang from Tier 4 Bouncers, level 500 Fenrich or inherit Big Bang through Chara World. Pass several strong enemy bills, add several Statistician Innocents to your weapon/armor or visit the Land of Carnage for some massive experience.
-OR-
Destroy the monster in front using any character you want, except Valvatorez. Have any character afterwards throw Valvatorez onto the spot where the now dead enemy was. Use Tyrant Flughude to take out all but the 4 monsters in the back. Destroy those this turn or next, if you want to grind Valvatorez leave him out, next turn they should move into a position where you can take the rest out in one hit. If not just have another character(s) throw the enemies into position.
The player can also throw the 4 enemies at each tip of the diamond formation into the enemies in the middle, combining them and creating a 3x3 formation like HoO4 from Disgaea 3. The player can easily kill the enemies in the 3x3 square formation with regular Big Bang, or a +8 Spell.
Another strategy, this time involving monster type characters, is to use Magichange to make Desco giant. This way, the reach of her attacks will be improved to the point that she can take out all but two of the monsters on the map with Yog Sothoth. This is a great way to level up not only Desco, but the monster she magichanged with as well.
NOTE: When using Magichange, the new weapon temporarily replaces your old weapon and all Innocents inside. To ensure that your Statisticians will always give their exp boost, move them to your bottom three equipped items, or bottom two if you plan to dual Magichange. Don't put Statisticians on your weapon!
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Using Tyrant Valvatorez, have him inherit Big Bang from someone and equip his No Life King evility. You will need two monster fusions so make sure that you are using the Fusion Weapon Lab and Dual Dojo Evil Symbols. You may also wish to equip three level 300 Statisticians and three level 300 Managers on his two bottom most pieces of equipment.
7Position Tyrant Valvatorez at the bottom of the enemy formation, closest to your base panel. Position a Nekomata (or any monster that can magi-change into a Fist) two spaces behind Valvatorez and fuse anything to it. Giant Magi-Change the now giant Neko to Tyrant Valvatorez and repeat with your second giant Magi-change.
Now attack with Big Bang and you'll notice you can attack twice. The first attack will destroy all the enemies, but with No Life King equipped, they will revive as ally units, your second attack will put them down permanently. Double the kills, double the rewards (EXP, Mana). Have Tyrant Valvatorez leading an expanded Training Ground and/or Aura Pyramid and set all enemies to max level (either the Cam-pain Bills or Cheat Shop if playing Disgaea 4 Return/Complete) while on Land of Carnage and 3 level 300 Statisicians and Managers, and you will reach level 9999 with every single attempt of this map.