In episode 3 you will come across a stage (stage 4) where you will be required to place your characters in a super fortress. Place in any 4 characters over level 12 and choose execute. You will instantly win if you do what I wrote above and get 1000 points getting all bonuses.
Making an Academy... (50% EXP boost to people put inside)
Reincarnate your people into Evil Carrots... (5th version of Evil Carrots get 80% EXP bonus at level 100)
Level 9-9 is pretty good for leveling to around 100, but slows down after about 75.
After you get to level 100 you can make special dungeons. Have your level 100+ Character equip a food item and make a free dungeon. This will make a 1 floor dungeon with 9 enemies that are twice the creators level in a 3x3 square.
If you feed one of your characters a food item in battle it'll get more exp when they kill an enemy. If you feed a food item to an enemy in battle, It'll increase the amount of exp they're worth.
In stage 3-4 there is a fortress you are supposed to invade. Rather than go inside, attack it from the outside. If your characters are strong enough, you should be able to damage it.(if not, train) If you can damage it with at least 5hp per hit, keep going until you destroy it.(this may take a while) Whoever delivers the finishing blow will be rewarded with about 400 mana.
Beat both Salome and Alec in stage 8-6.
You have to get level 200, 9000 mana. Wish "Fight against Babylon." Available in chapters 2-8. Defeat Babylon.
Get level 300, 20000 mana. Wish "Fight strongest person in game." Beat Baal.
Have a character at Lv.160 or above and have at least 9000 mana. This will open the dungeon to face off against Seedle.