In the Ancient Cave on the 17th floor is a floor boss called the Parasitic Cell, if you've learned Miracle Hit and are above level 23, you should be able to defeat it by using Miracle Hit every turn. It has 1250 HP so you'll be fighting for a while. If you win, you will receive 20100 EXP.
Alchemists
During your adventure, you will need to search for Alchemists to learn how to create special items in the Blacksmith Building in Gruberik. The Alchemists are disguised as animals, people, and monsters.
Best Accessory
The Egg Ring is the best one you can wear. If you wear it on your character, you can attack two times. If you attack with rapidfire, you can attack three times. Now, no one can stand in your way. You can find it on floor 59-60 or you can get it by killing the boss on floor 60, to beat the Ancient Cave.
Best Armor
The Lucinia Armor armor is the best Armor that you can find. When the enemies damage your hit points, your HP and MP are automatically replenished, but sometimes it does not do anything. You will also see that miracle is being used. You can get the Lucinia Armor on the 36th to 60th floors.
Best Helmet
The Divine Helmet is the best that you can wear. It is found on the last two floors of the Ancient Cave.
Best Shield
The Divine Shield is the best that can be found in the game. You need some luck in the Ancient Cave to get it. It is on floor 59 to 60.
Best Weapon
The Gaia sword is the most powerful weapon. You can find it on the 60th floor of the Ancient Cave. You will need some luck to get it. When equipped, the Gaia sword boosts your attack power a great deal.
Easy Gold in Ordens
Once you reach the town of Ordens go to the item shop and buy as many Blue Teas as possible for 100 gold each.
Then you can sell them back for 150 gold each. You can make between 50 and 4450 gold each time.
Easy Money
Go to the town of Ordens. Go to the item shop and buy all the Blue Tea you can for 100, then sell them back for 150. You can buy 99 for 9900, but when you sell back 66 you gain back 9900 plus the other 33 that you sell. Continue to buy and sell until you have enough money.
Easy Training For Main Character
After you can enter the Ancient Cave, buy yourself a suit of Bronze Armor and the best weapon that you can buy at the moment, kill off your party members and get have the main character train as a Swordsman. Get him to level 10 and enter the Ancient Cave, if you can defeat the boss on floor 9, you'll get 6000 experience, make sure you have a providence because the monster on floor 12 will be able to do 80+ damage to you. I was level 25 and it was doing 97 damage to me. Repeat this process to gain levels very quickly. It's also a good way to master classes.
Infinite Nectar
Go to the blacksmith in Gruberik. Make sure you have the ingredients for a Nectar (and found the alchemist). Make a Nectar. The blacksmith will make the item like normal, but you won't lose the ingredients! You can get infinite Nectars at no cost.
Lots Of Speed Sources
If you find an enemy called Hawk, fight it constantly, it has a chance of dropping Speed Sources which boost your speed permanently by 2-6.
Master All Jobs Quickly
After finishing Border Forest, go back to it from the east side (the one you exited from; do not bring any monsters). Rope your way across the pit, go into the opening in the trees at the top,t hen through another opening at the right. You will find four rocks surrounding a bush. Break a rock, then cut the bush to fall down into a room with Green Cores. These monsters give 2525 experience points each and appear in groups of two or three. They have low HP, but very high defense. First, fight a few battles and kill all your party members except for one. Have him kill as many Cores as he can before they run away. Use Chance Hit, Virus, or any other group attack spells except for Frost. For maximum effect, make sure the character has an attack power over 120 and has learned the Rogue skill Rapid Fire. This allows you to take out all the Cores in one hit. When the room is cleared, exit and reenter to find the Cores again. When a character has mastered all the jobs, revive another character and kill the first. Then, repeat the process. This is the fastest and easiest way to master all the jobs and will make clearing the Ancient Cave a breeze for Eldin.
Sacrifice Glitch
Sacrifice kills the enemy and the user. However, there is a glitch. If you use Sacrifice on yourself, you heal 999 HP.
Using Two Characters In The Ancient Cave
In the Ancient Cave, use a Cave Disc and capture a monster that you want to use there. The monster can also assist you in the Ancient Cave. The best monster to capture is Cyclops Dragon, if you level it up with Power Source. Teach Cyclops Dragon with Octo Strike and you will be invincible. Battling through sixty floors will be a lot easier.