Complete the game once, save your game and load your completed game save. A new map, The Graveyard, will appear. Now go to the colosseum and fight through 10 battles. You will receive a piece of equipment (a pendant) that nobody seems to be able to equip. Visit the Graveyard with the pendant, and a special event will occur.

After beating the game, you will be prompted to save. Do so and load your saved game. Your game will be in the last chapter, right before you enter Paris Castle.

A free stage, Cemetery will appear. The enemies are not that bad but it does contain really good loot. Here are the rewards:

Durendal (sword)
Devil's Frock (armor)
Holy Shield
Gem of Darkness (Roger)

The strongest armor in the game is one of the hidden item locations in this ttage and is MISSABLE; meaning it is only available on your first visit to the cemetery so make sure you grab all the items. (Use Colet's Treasure Hunter or Rose's Treasure Lover skills to find the items easily)

During Round 7 of the Colosseum's 3rd season (Beat it twice), several item locations will be available. These locations contain the ultimate weapons for your characters and the rarest skillstones that you cant just bind or find anywhere else. If you can make your way up to this round, you can just clear it, return to the map, save and repeat the process.

Deathbringer (sword): Range +2
Gae Bulg (spear): Mobility +3
Lucifer (axe): Three Rounds
Tsukikage (dagger): Attack +30
Caduceus (staff): Accuracy +30
Rose Whip (whip): Evade +30
Bow of Atremis (bow): HP +300 / MP +150

The best way to train your characters is equipping them with Exp Bonus IV (Exp Bonus III+Exp Bonus III). This skillstone will allow characters to get 300 experience! Exp points are relative to the level of the target and the character. When lower level characters deal damage to higher level enemies, they gain more exp. But if your character is higher than the target, the minimum exp pts that they can get per attack is 5. So with the Exp Bonus IV equipped, characters can gain 15 pts per hit on normal attacks even on weaker enemies.

Next, equip them with Three Rounds. Normally, after three successful hits, characters can only get 15 pts. Now with Exp Bonus IV, players can get a minimum of 45 pts if all three attacks connect. Since exp is based on every successful hit (even if the defending enemy has blocked it), area-damaging skills like Sweep, Compass, Salvo, etc has the possibility to yield over 100 pts per attack.

Where to train your characters:

Some of my suggestions where you can train while reaping rewards are the following. Chalons, Grandgris Pass and Voldor Temple. Chalons has weak enemies, but will reward you with ExpBonus II upon completion, along with other good rewards. Four Exp Bonus II skillstones = Exp Bonus IV. After collecting at least 5 (your choice) then you can train next at Grandgris Pass. Grandgris Pass is a good place to train because of several reasons. First is that enemies here have higher levels here compared to the other free stages. The Shadow Knights have really high HPs and fairly weak attacks so they make good targets for multiple attacks. Second, the dragon on the starting point is a great target for area of-effect attacks and spells; thus chances of earning higher exp pts. Third, the bridge makes a good bottleneck position, thus piling up enemies and hitting them with attacks.

The third season of the Colosseum is the hardest to clear since the enemies will have a 20 level boost from your last visit. Here are some tips on who to bring and how they should be set up:

Equip the best skills and equipment you
have and make sure to train your fighting team solely. Equip each member of your team with HP Recovery III, HP+150, Three Rounds and if possible, Mobility +2. You may consider a team with the following:

Tank Preferably Rufus. Why? He has the highest HP and attack. Equip him with a Lucifer Axe and the best armor you can get at the moment maybe the Firedrake
Armor from Tiamat on the Free Stage of Voldor Temple. For skills, Helm Splitter,
Desperation III, Mobility +2, Three Rounds, HP Recovery III and HP +150 will be the best choices.

Spearman Gilles of course. Gae Bulg is the ultimate spear so equip it to him. For skills, you can choose any red skillstone as his special attack, Piercing Power III to deliver heavy damage to distant targets and the basic skills listed above.

Healer Richard or Claire; for a healer, the most important spell is Revivify. This spell will allow you resurrect fallen members. You can equip him with HP+150, HP Recovery III, Mobility +2, Revivify and you can choose two more skills. Id prefer an attack spell (avoid using the ultimate spells since they take too much time to cast) and a healing spell (Healing Wind II is good but if you really need to heal often, just bringing in Heal II is fine) Mobility +2 will allow your healer to run into a safe location if cornered.

Rogue or Thief A high level Rogue (Colet) or Thief (Rose) can evade almost all attacks, except magical and special attacks. Not to mention that though they dont have that high attack ratings, HP and defense, their critical hit, accuracy and evasion are so pumped up that they can be good choices of producing Burning Auras without getting damaged by enemy counter attacks. They can provide much needed distraction especially when a vital character (such as the healer) is in risk of getting cornered.

For the last member, you can put in another tank or spearman. I just didnt include archers because even with the Bow of Artemis and Attack +30 equipped, they will just deal very little to no damage at all against bosses. You chances of defeating enemies quickly is by generating strategically positioned Burning Auras then attack them. Having the Godspeed skill equipped to your main attacker can also make quick work on enemies.