In the Ancient Cave are blue treasure chests. Those blue chests are the only items that you will be able to bring out of the Ancient Cave other than the Iris Treasures. All other items in the red chests will be taken away from you on your way out. Note : you can also bring the blue chest items back in the Ancient Cave. The fun part is that if you got a catfish jewel , or another item dropped by a monster and that it also happens to be a possible blue chest, you won't have it taken away from you; you'll still have it in your inventory and you're gonna be able to use it in the Ancient Cave. Beware of blue and red mimics. The blue ones have over 300 HP each and can hit pretty hard.Notice the slight coloration difference between the normal chests and the mimics. Also, if you see 2 blue chests together like in the blue mimic picture (click on the link) or right in front of a door, its suspicious.

First I suggest that you have Maxim, Guy, Dekar and Selan in your party. When you enter the Ancient Cave, all your characters will be downgraded to level 1 and you'll only have 10 potions in your inventory. The trick to going through the ancient cave is to find many blue treasure chests on many trips. You're also going to need some luck because you're going to need the "absorb" spell to steal enemy MP and thus not run out of MP or MP restoring items and the "strong" spell and some good equipment in the red chests to compensate for what you couldn't find in the blue chests. Strong will cure a lot of HP for 3 MP, which is very practical. The key weapons to winning are the Dekar Blade and the Gades Blade. The Gades Blade is a blue chest item, the Dekar blade is not. At the bottom of the Ancient Cave is the Jelly Juggernaut and you have 3 rounds to kill him. Before you fight him, he'll ask you if you want to fight or not. If you choose "not fight", he'll dissapear until you step back on the spot that made him appear in the first place. This gives you time to prepare yourself. In the first he heals your HP, second your MP and third he does nothing. After that, he hits himself and you get nothing. To beat him, you need to use the Dekar balde's IP power to cut his HP in half and the Gades Blade's octo strike to inflict major damage. With Maxim and whatever other character you'll have , use your strongest attacks. If you manage to beat the Jelly Juggernaut, you'll find out he's an Iris treasure and you'll also get the key to the door in the entrance of the cave. Note : you'll have to speak with the girl to see that he's an Iris treasure because he isn't in your inventory (she'll take him from your guy and bring him to the counter). He will be on display though...

If you really wanna be cheesy, kill your guys and you'll win. Its weird, but it works. Look at my status screen! You'll still get the key and the Iris treasure.

Note: In the lower levels of the Ancient Cave are the strongest monsters in the game! Monsters you will NOT find anywhere else in the game, monsters which can wipe out your party VERY easily. Be sure to fight as many monsters as you can to gain the highest levels possible to have the best chance against these beasts.

On your way down the Ancient Cave you will also encounter strange bushes. Cut them to reveal HP restoration points. You won't find MP restoration points though.

To get out of the Ancient Cave, you need the Providence, which is found around the 20th level. Make sure you don't miss it or you might regret it. To uncurse items, you will also find Curselifers. Use it on a character who is equiped with a cursed item to uncurse it.

However unpractical it is for the fight with the Jelly Juggernaut, you should use the "Shaggy" capsule monster because he'll heal your characters throughout the journey down the Ancient Cave.

If you manage to collect all 8 of the Iris Treasures, bring them to the lady in the basement of the tavern in Gruberik. Nothing special will happen, but as you bring her Iris treasures, she'll put em on display and congratulate you when you get them all.

Note about the Dark Mirror from Onion Kid: The one shown in the list is the cursed item. The uncursed item is not a blue chest, so don't uncurse it in the ancient cave if you want to take it outside. This is the only cursed blue chest item. Also, if you walk into the cave wearing the cursed version, it will be taken off and put in your inventory.

Special thanks to Onion Kid for the missing Blue Chest info!