Defeat the Unversed
Upon arrival, you must deal with a group of Unversed. Four new enemies are introduced to you here: the Buckle Bruiser, a stronger version of the Bruiser, the Vile Phial, which can prove quite irritating despite its weakness and small size, the Axe Flapper, an aerial Unversed capable of launching projectiles at Terra, and Yellow Mustard, a Thunder-dishing variation of the fiery Red Hot Chili and the icy Blue Sea Salt. Buckle Bruisers, like Tank Topplers, can only be attacked from behind; attacking from the front will only break Terra's attacks. Take note that Strike Raid will have no effect on this Unversed even if you begin the attack from behind, as Terra's attack will only be broken when his Keyblade makes its way back to him. To incapacitate them easily, use magic commands such as Zero Gravity, Magnet, or Aero. The Vile Phials will occasionally float around off to the side, momentarily casting Poison on Terra and healing itself as well as allies. Take them out quickly to avoid becoming poisoned (their Cure spells are weak enough that you don't have to worry about them). Axe Blasters, like Vile Phials, play more of a supportive role to their more powerful comrades, though they are much more aggressive, launching blades of wind at Terra that home in to his location. Like Archravens, they can be knocked out of the sky with aerial combos.
Do what you must to defeat all rounds of Unversed. If you ever find yourself struggling for HP, break one of the nearby pots for some emergency orbs. After the battle, Terra will meet Hercules and learn about the tournament. Enter the Coliseum Gates to meet Hades, then pick up the treasures scattered around the area; a Mega-Potion can be found in a corner to the left of where you entered, a Mega Attack Recipe can be found behind the pillars to the left of the coliseum entrance, and Fire Strike can be found behind the statue's foot to the right. Enter the Vestibule and open the chest for a Map, then speak to Hades to enter the tournament.
Terra's trek through the tournament begins with rounds of matches against Unversed. These matches are timed, but fortunately, you will only ever have to deal with a few Unversed at a time. If ever you seem to be having trouble, equip commands that effectively perform crowd control such as Zero Gravity or Magnet, as well as quick offensive attacks such as Thunder Surge. Lastly, don't forget to make use of Counter Hammer, Command Styles, and Shotlock.
The first round consists of three Scrappers, which should be dealt with relatively easily. The second round should also be cleared without trouble, with only a Vile Phial and an ordinary Bruiser in your way. Take out the Vile Phial first, then use any offensive commands available to quickly take out the Bruiser. The third round consists of three Spiderchests; this may prove a bit more difficult due to their ability to burrow into the ground, delaying their inevitable defeat. Begin with an attack that can incapacitate all three at once to stun them all quickly, and use Shotlock if necessary. The fourth round consists of a single Buckle Bruiser. Clear this round quickly by staying behind it, and save all Zero Gravity and Command Style attacks for the next round, consisting of five Shoegazers. The sixth round also is no pushover, made up of a series of aerial enemies (one Axe Flapper, two Red Hot Chilis, two Blue Sea Salts, and two Yellow Mustards) that can easily evade Terra's attacks. Fortunately, they are all relatively weak, making them easy Shotlock targets. The seventh round consists of three Buckle Bruisers; again, Zero Gravity comes in handy here, with the ability to make all three utterly defenseless.
The eighth round has Terra dealing with two Chrono Twisters and two Monotruckers, a group which shouldn't put up much of a challenge after the previous rounds. The penultimate round consists of one Bruiser and five Mandrakes, and the final round of Unversed has Terra deal with thirty Jellyshades in thirty seconds. Again, this is all easily doable with Zero Gravity, Command Styles, and Shotlock. After clearing all rounds, Terra obtains Sonic Impact and a shot at the finals. Speak to Hades for a boss fight.
Zack begins the battle with only a couple of attacks. First, he swipes his sword into the air in an attack reminiscent of Aerial Slam, launching Terra into the air if caught and slamming him back down with a shockwave. Second is his long-range attack, which he only uses if Terra distances himself from the soldier, sending a trail of darkness Terra's way that can be easily dodged. Although there is a great amount of power behind these attacks, Zack is easily caught in combos and can also be caught off-guard with projectile or long-range attacks, such as Blizzara or Zantetsuken. After taking out all of Zack's HP, the battle becomes serious and enters its second phase.
Zack takes a serious step up in strength with the power of darkness on his side. Not only does he hit harder, but he also has more attacks available to him. Zack begins the battle by sending out a dark shockwave before giving chase, teleporting to Terra's location with the accompaniment of constant attacks in a battle style reminiscent of Sephiroth's. You can either combat this by blocking, which may prove difficult due to Terra's Guard only protecting his front, or using Slide constantly, circling around the arena to avoid Zack's barrage of strikes. He will finish off the long-winded attack with the familiar shockwave, which can also be dodged. If you'd rather forego the dodging altogether, use Shotlock as soon as the battle starts; it should provide enough invincibility frames to last the duration of the attack. Regardless of the strategy you use, when Zack raises his sword in the air surrounded by darkness, prepare to avoid the attack once again.
Another of Zack's attacks is a meteor shower, which will stay close by Zack; Slide away from him as soon as you see them hit, then take advantage of his vulnerability and utilize a far-reaching attack. After every one of these long and strenuous actions, Zack will tire and simply slump over, giving Terra another opportunity to strike. Keep in mind that he can be caught in a combo just as easily as before, but he can also break out of it. Once More (created through two max-leveled Blizzara commands and a Pulsing Crystal) is a useful ability to have for the entirety of this battle. Defeat him for an increase in deck capacity and, after some scenes, the Mark of a Hero Keychain, which boosts Strength as well as the power of critical hits.