Zack

Zack is a character in Kingdom Hearts Birth by Sleep that appears in Olympus Coliseum and is the only Final Fantasy character to appear in the game (other than the Moogles). Zack strives to be a warrior, teaming up with Ventus to fight off the Unversed. Zack meets Hercules through this Unversed attack, becoming friends with Ventus and harboring a possible crush on Aqua or just flirting with her.

Kingdom Hearts Birth by Sleep
Zack appears in Olympus Coliseum looking for Phil, who is known for training people into heroes and hopes to become his trainee. He meets Hercules and Ventus during an Unversed attack and shows his skill in front of Phil. Since Phil only trains one trainee and already has Hercules, he "decides" to form a competition between the two boys to help make his decision: Hercules or Zack.

During Herc and Zack's showdown, an army of Unversed appear in the city of Athens and Ventus goes to deal with them. Not wanting their friend to get hurt, Herc withdraws from the competition just one second before Zack does. By the time Zack arrives, the monsters are already defeated. Phil then arrives and tells them that part of a hero's important quality involves the will to do what is right and quick acting, and, since Zack withdrew after Herc, Hercules is once again "becomes" Phil's trainee. Though disappointed, Zack faces his defeat cheerfully.

During one of these tournaments, Terra arrives in the Coliseum and Hades tries to find a way to make Terra succumb to darkness. When Zack walks by, Hades uses the darkness in his heart to control him. When Terra reaches the final round, Zack becomes his opponent but is defeated. As Terra turns to leave, Zack gets up and attacks again, this time using the power of darkness and more powerful attacks. Terra wins again, freeing Zack from Hades control. After their second battle, Terra helps Zack up and he introduces himself. Zack tells Terra he reminds him of a certain hero he admires by his attitude, though Terra says he isn't one. Zack doesn't listen and says being a hero or not isn't something you choose yourself, and after watching their battle, now both the crowd and him consider Terra a hero. Before Terra leaves, the two promise each other a rematch, one where Zack would use his own strength.

Later, Zack meets Aqua while she's talking with Phil and Hercules about Terra. As Zack talks about fighting Terra after their match, Aqua is confused, but Phil explains the rules and about the East and West blocks. Both Phil and Hercules leave, and Zack explains to Aqua how he met Terra and about how Hades controlled him with darkness.

Both Zack and Aqua fight in their match, and Zack loses. Zack accepts defeat cheerfully, and Hades appears. Hades comes to check out what happened, and Zack is angered to see him again. The god leaves after insulting Terra and admitting he would be the to fight in the title match, which Zack tries chasing after him. Zack now is disappointed in his loss, but he tells Aqua to take revenge for him and Terra.

Aqua shows up for her match, while Zack watches from the stands. Hades shows up with the Ice Colossus, saying the rules allowed back-up. Zack immediately comes to Aqua's aide, but she tells him to leave both of them to her. She wins, and the pair leave the Coliseum together. Zack wants to celebrate her victory, so he asks her on a date. Aqua shakes her hands in embarrassment, saying she's on a journey and she's still a trainee. Zack then makes Aqua promise they'd go on a date as soon as he became a warrior. Although Aqua says she can't make such a promises, Zack doesn't listen and says now he's gotta get serious about his training and he runs off.

In the ending credits, Zack is seen leaning against the door to Olympus Coliseum while watching Phil train Hercules. A black feather flutters behind Zack, and he looks around in surprise. All that is then seen of him is a single black feather drifting down where he once stood.

Appearance
Zack sports his original hairstyle of short, thick black spikes with bangs framing his face. His eyes are a bright blue. Due to his appearance in Olympus Coliseum, he wears armor similar to that of Hercules, though his is grey, as opposed to Hercules's orange. Other than this additional armor, Zack wears his SOLDIER uniform of two silver pauldrons, black gloves, a brown guard over his abdomen that is worn over the armor, two belts over the aforementioned guard, and his blue pants and turtleneck, significantly brighter than Zack's original navy-colored clothing.

Zack's brown, knee-high sandals also bear the vague design of his original black, knee-high boots, and he wears black socks underneath them. Small parts of his outfit have had swirls added to them and his physique is slightly different, likely to fit more with the style of Olympus Coliseum. Finally, Zack carries his original SOLDIER sword as a weapon. The SOLDIER's logo is seen both in his sword and in his brown guard, just above the belts.

Zack wore a Gladiator-style helmet during the first fight against him.

Fighting Style
Zack is fought twice within Terra's story and once in Aqua's story. You must talk to Hades in the Coliseum Lobby to fight Zack. He is a very strong opponent and can be very difficult to defeat if not prepared properly. His attacks in the first battle do mild damage. These attacks include a spin-slash attack, a quick 3-hit combo, a jump ground attack, and a Dark Braver attack.

In the second battle, he is much quicker. His attacks have been powered up and can be very deadly. He keeps his four original attacks including two new ones, a high speed slash technique and a meteor attack. To keep up with Zack, D-Link with Ven for higher speed or D-Link with Aqua to have greater magical capabilities.

D-Link
Zack becomes a D-Link for Terra, Ventus, and Aqua after their separate encounters. While in link with Zack, they can perform powerful blows with increased speed as well as create wave beams to blow their enemies aside.

Origin
Zack Fair first appeared in the English and International versions of Final Fantasy VII, along with many others, as a minor character, yet pivotal towards Cloud before appearing as a full-fledged character in the prequel, Crisis Core: Final Fantasy VII. Having wielded the legendary Buster Sword before Cloud (after Angeal Hewley passed it on to him), Zack was an aspiring 1st class member of the elite troop known as SOLDIER. He also played a role in Advent Children.

Trivia

 * Zack is the fourth Final Fantasy character to be introduced at Olympus Coliseum (following Cloud, Sephiroth, and Auron), and idiomatically the seventh Final Fantasy VII character to appear in Kingdom Hearts.
 * The way Zack asks Aqua out on a date may be an allusion to how he does so to Aerith in Crisis Core: Final Fantasy VII.
 * Zack's tutelage under Phil to become a "hero" at a young age alludes his original counterpart under the tutelage of his mentor in Crisis Core: Final Fantasy VII with a dream of becoming a hero as well.
 * During the credits sequence, Zack leans against the door at the Coliseum just as he does at the end of Final Fantasy VII: Advent Children (Final Fantasy VII: Advent Children Complete).
 * Zack is the second Final Fantasy character to appear in the series with his own theme; a remix of the main theme of Crisis Core, known as Successor, the first being Sephiroth.
 * Throughout Kingdom Hearts Birth by Sleep, Zack can be seen doing squats, a well known hobby of his in Crisis Core: Final Fantasy VII.
 * Some of Zack's attacks are variations of DMW limits used in Crisis Core. These include Meteor Shots, Octaslash and Rush Assault. He also uses a variation of Cloud's Braver Limit Break, which greatly resembles the way Zack uses the Jump Materia in Crisis Core.

Zack