Arena Mode

In Arena Mode, there is a total of 13 matches you can participate in. These are not, however available right off the bat. In order to compete in all but the first match, you must reach a certain Arena Level. This is displayed right above the player on the left side at all times while in the Mirage Arena Lobby. These are perhaps some of the most challenging fights in the game. You will face not only some familiar bosses from the game, but you will face 5 new bosses that are difficult nuts to crack.
Each of the different matches comprises of a set of 3-9 rounds of combat. Each of the 13 battles, save only for two, end with a tough boss (s) to face. They are also set with a difficulty rating, thus allowing you to see how difficult the battle may be before entering it.
You will fight throught the battles, similar to the Colesium matches in Kingdom Hearts I and II. You should be set with Deck Commands, that can easily eliminate groups of enemies, while also saving some room for a Curaga or two. As the battles progress, you should consider setting in a couple of more Curaga's. You should also get your Fire, Thunder, and Ice abilities. Second Chance and Once More are a must have in this arena as well. Make sure you are well set before each individual fights. Set your decks carefully, and prepare accordingly. These bosses you have fought before are very much the same that they were in the game, but they are far tougher than before. The new bosses are far more difficult. They will rip you to shreds if you are not at a high enough level, or prepared for the fights.
Below is a list of the 13 battles, their rating, what level you need to unlock them, as well as the bosses you face and rewards you gain.

Battle	Bosses	Lv	Rank	Rounds	Medals	Rewards
Day of Reckoning	Iron Imprisoner I	1		4	75	-
Wheels of Misfortune	Cursed Coach	1		4	90	A: Max HP +5
Weaver Fever	Wheel Master	1		4	120	T: Max HP +5
Sinister Sentinal	Iron Imprisoner II	3		5	150	T: Xehanort's Report 5 V: Sky Climber Command Style
Dead Ringer	Mimic Master	5		5	180	T: Darkgnaw Keyblade V: Max HP +10
Combined Threat	Trinity Armor	7		6	210	A: Sky Climber Command Style
Risky Riches	-	8		3	105	-
Harsh Punishment	Iron Imprisoner III	10		6	300	-
A Time to Chill	Hades/Zack Ice Titan	13		8	375	V: Max HP +10 A: Max HP +10
Treasure Tussle	-	15		3	240	-
Copycat Crisis	Mimic Master	17		8	450	T: Max HP +10
Keepers of the Arena	Iron Imprisoner III Iron Imprisoner IV	20		9	500	T: Ultima Cannon S.L. V: Multivortex S.L. A: Lightbloom S.L.
Villain's Vendetta	All previous bosses	30		8	???	All: Ultima Weapon Keyblade

Arena Bestiary

Below is the complete bestiary for the arena bosses. By each boss name is the name of the arena match they are in. Most all of the bosses are faced in two different matches, and one is found in three. They are the same in each fight, just the attack and defense are a bit higher for the later fight.

Iron Imprisoner I (Day of Reckoning) HP 1200 Strength 14 Defense 3 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything	Iron Imprisoner I (Villain's Vendetta) HP 1200 Strength 40 Defense 20 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything
Iron Imprisoner II (Sinister Sentinal) HP 1250 Strength 21 Defense 10 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything	Iron Imprisoner II (Villain's Vendetta) HP 1250 Strength 40 Defense 20 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything
Iron Imprisoner III (HArsh Punishment) HP 1300 Strength 24 Defense 13 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything	Iron Imprisoner III (Keepers of the Arena) HP 1300 Strength 36 Defense 19 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything
Iron Imprisoner III (Villain's Vendetta) HP 1300 Strength 40 Defense 20 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything	Iron Imprisoner IV (Keepers of the Arena) HP 1500 Strength 36 Defense 19 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything
Iron Imprisoner IV (Villain's Vendetta) HP 1500 Strength 40 Defense 20 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything	Mimic Master (Dead Ringer) HP 1800 Strength 19 Defense 7 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to all but Stun, Ignite, and Poison
Mimic Master (Dead Ringer) HP 900 Strength 30 Defense 16 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to all but Stun, Ignite, and Poison	Wheel Master (Weaver Fever) HP 1750 Strength 19 Defense 7 Elemental Weakness Physical x1.0 Fire x1.5 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to all but Ignite and Poison
Wheel Master (Villain's Vendetta) HP 1750 Strength 40 Defense 20 Elemental Weakness Physical x1.0 Fire x1.5 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to all but Ignite and Poison	Cursed Coach (Wheels of Misfortune) HP 1200 Strength 16 Defense 5 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to all but Stun
Cursed Coach (Villain's Vendetta) HP 1200 Strength 40 Defense 20 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to all but Stun	Trinity Armor (Combined Threat) HP (Head) HP (Limbs) 1350 1000 Strength 24 Defense 13 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything
Trinity Armor (Combined Threat) HP (Head) HP (Limbs) 1350 1000 Strength 40 Defense 20 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x1.0 Status Resistance Immune to everything	Ice Titan (A Time to Chill) HP 1600 Strength 30 Defense 16 Elemental Weakness Physical x1.0 Fire x1.25 Blizzard x1.0 Thunder x0.75 Dark x0.75 Status Resistance Immune to all but Ignite
Ice Titan (A Time to Chill) HP 1600 Strength 30 Defense 16 Elemental Weakness Physical x1.0 Fire x1.25 Blizzard x1.0 Thunder x0.75 Dark x0.75 Status Resistance Immune to all but Ignite	Zack (A Time to Chill) HP 600 Strength 30 Defense 16 Elemental Weakness Physical x1.0 Fire x1.0 Blizzard x1.0 Thunder x1.0 Dark x0.5 Status Resistance Immune to all but Stun, Freeze, Poison, Ignite, and Zero Gravity
Hades (A Time to Chill) HP 1000 Strength 30 Defense 16 Elemental Weakness Physical x1.0 Fire x0.5 Blizzard x0.5 Thunder x0.75 Dark x0.75 Status Resistance Immune to all but Freeze