La Pucelle

The game mentions that experience can be obtained by all participants in a battle, but it does not mention that the experience is divided. If you really want to level up your character, you should have them attack lower level character by themselves. You will get more experience faster by doing this rather than killing stronger enemies as a group.

Enter and make a Dark Portal of 300. On the 10th floor, kill a Demon Overlord over level 500. Note: Make sure the enemies on the first floor are at least 300. Afterwards you can run or finish the level and watch the special ending, and get a new title for Prier and the Warp Engine item.

Defeat twenty Demon Overlords over level 500 and one Demon Overlord over level 700 to unlock another title for Prier, and the Light Year Cannon.

Go to the Rosequeen Shop in Pot au Feu City then go to the shop owner. This trick might require some patience, but is well worth it. Buy some Change-ups or any cheap item in the shop, then do the survey. Do any of the four questions and sell the item back. Keep doing this until the girl asks "If you had one wish, what would it be?". Once you have that, you can get any of the triple effects.

These two bosses were not in the original USA or JAP NTSC releases, but were added to the Japanese re-release and the PAL release.
Please note that, unlike Capricorn Baal, these forms are NOT obtainable.

If you forgot how to make monsters come to your side(convert), then read the following: First, purify the monster chosen by you to be a part of your team. Second, keep purifying the monster until the box at the top when puryifing says, "Will convert no matter what". Then kill the monster and after you kill it a box will appear saying such and such monster has joined you. If you have already converted one type of monster and want to convert a different monster of the same kind, you will not have to purify it until the point where it says "Will convert no matter what". Make sure you consistently train you monster or it will dislike you and run away.

Normally you can only get one of these by purifying and killing Baal at The God's Ordeal. If you return to the map afterwards, Baal no longer has the Robot Suit equipped.
The exception to this is if you have a full inventory when you purify and kill him. Instead of dropping the Robot Suit, Baal joins your party with it equipped. Now when you return to the map, the Baal there still has a Robot Suit. You can then repeat the process to get as many Robot Suits as you like.
The glitch also works on the Zombie King in the Cave of Trials, should you wish to get multiple Godhands. However, you will not be able to access The God's Ordeal until you get the Godhand in the normal way.
Note that this glitch was partially fixed in the PAL version, preventing you from getting more than one Robot Suit. You can still use it to get multiple Godhands though.

In chapter 4 you must defeat the gaint whale enemy the first time you encounter it. You can only do this the first time out of the two times you enter a battle with it. After you complete chapter 4 you'll net yourself the a special ending rank, 50k price and the Angel Shoes.
Besides using a cheating device the Angel Shoes can only be gotten this way so if you don't do this you'll miss them for good.

Go into the item shop and buy ALL the items they have, this will cause the merchant to have items delivered from their Dark World branch. select buy again to see the new items. To get the Dark World Items again you will have to buy out all the normal items again.

When your in battle, if one of your characters can reach the base panal, and your character can't do anything, you can make it walk to the panal and you can switch your characters. It will not heal your characters. You can do this so your characters won't waste their turns doing nothing. Switch wisely. Once they step on the panal, they don't move as far because it is as if they started over from the begining.

Note: This is only available in the European version of the game. Defeat Phantom Baal (Eringa) to unlock True Baal Castle to the left of New Baal Castle on the map.