Zack

Zack is a character in Kingdom Hearts Birth by Sleep that appears in Olympus Coliseum and is the only Final Fantasy character introduced in the game. Motivated by Terra, Zack strives to be a hero, 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. He also sought training under Phil to become a hero, but Phil chose to continue training Hercules in the end.

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. Phil enters them both in only one of the two main blocks in the tournament, since there was another strong contender in the other block (presumably Terra). To be fair to Zack, Phil refuses to train Hercules until he "wins" his match with Zack, prompting Hercules to train with Ventus.

During Herc and Zack's showdown in the semi-final round, an army of Unversed appear in the city of Athens (the Town Near Thebes) and Ventus volunteers to deal with them so as not to ruin Hercules and Zack's match. Not wanting their friend to get hurt, Herc withdraws from the competition just one second before Zack does. By default, Zack wins the match. However, 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 Hercules, Hercules once again "becomes" Phil's trainee. Ventus secretly asks Phil whether he ever intended to stop training Hercules at all. Phil admits that Hercules was in a rut and needed their competition, but Phil acknowledges Zack's potential. Though disappointed, Zack faces his defeat cheerfully.

In the meantime, Terra arrives in the Coliseum, and Hades tries to find a way to make Terra succumb to darkness. Frustrated by Terra's advancement in the tournament, Hades spots Zack entering the Coliseum and 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's 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 denies the compliment. Zack doesn't listen and says being a hero or not isn't something you choose yourself, and after watching their battle, 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 is talking with Phil and Hercules about Terra. As Zack talks about fighting Terra in the finals after their match, Aqua is confused, but Phil explains the tournament rules and about the East and West blocks (the two main blocks mentioned earlier). Both Phil and Hercules leave, and Zack explains to Aqua how he met Terra and about how Hades controlled Zack with darkness and how Terra saved Zack. Aqua is relieved to hear this news.

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 fought in the title match, while Zack tries chasing after him. Zack is now disappointed in his loss, having lost potentially his only chance to fight Hades after Hades tried to use him, but he tells Aqua to take revenge for him and Terra.

Aqua shows up for her match, while Zack cheers from the stands. Hades shows up with the Ice Colossus, claiming the rules allowed back-up. Zack immediately comes to Aqua's aid, but she tells him to leave both of them to her. She emerges triumphant, 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, blushing, 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 becomes a true hero. Although Aqua says she can't make such a promise, Zack doesn't listen and says now he has to get serious about his training and he runs off outside the gates.

Some time after the battle at the Keyblade Graveyard, Zack is seen with his familiar habit of leaning against walls. He leans by the door to Olympus Coliseum while watching Phil train Hercules. A black feather is shown fluttering beside 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's concept art for Kingdom Hearts Birth by Sleep has a visible outline of the Buster Sword upon his shoulder, but the blade does not appear in the game proper.

Zack wears a Gladiator-style helmet during Terra's first fight against him.

Personality
Zack's personality can somewhat be compared to Ventus's. He is happy, cheerful, and good at making new friends, and he quickly befriends Terra, Aqua, Ventus, Hercules, and Phil. He is also shown to be a good sport, seen once Phil chooses to train Hercules, and again when he is defeated by Aqua. Zack does have his fair share of patience and seems to take disappointment rather well, dismissing it as "lousy luck". An example of this would be when Phil picked Herc over him. Zack's biggest ambition is to become a hero, much like his Final Fantasy self, and it proves to be his primary motivator. He can be very persistent and earnest, chasing Phil around town, and he relentlessly pursues his dream of becoming a hero, so much so that Phil nicknames him "Captain Eager".

Fighting Style
Zack is fought twice within Terra's story and once in Aqua's story. You must talk to Hades or Phil in the Coliseum Lobby to fight Zack. He is a very strong opponent and can be very difficult to defeat if not prepared properly. Terra fights Zack both normally and when possessed, while Aqua fights him only normally.

Zack easily uses his sword in combat, specializing in quick one-handed and double-handed strikes. Zack is agile and quite capable of backfilps, ten-foot leaps and fast strikes, which he excels at. He tends to use hit-and-run tactics, back-flipping to a safe distance when done. He is also able to use Dark Braver and a light based spell, which involves swinging his sword to channel energy on the ground.

When controlled by Hades in the second battle, Zack becomes a killing machine. He is able to use "Hero's Pride", which consists of lethal high speed slashes while teleporting. He can also call down a slew of meteors, as well as fire a dark based version of Dark Braver. He is much stronger and can prove to be a tough opponent for Terra.

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, and the Blade Beam Limit Break that Cloud used in Final Fantasy VII.

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 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, Zack was an aspiring 1st class member of the elite troop known as SOLDIER owned by the energy company Shinra and aimed to become a hero.

Crisis Core -Final Fantasy VII- portrays Zack's journey. Realizing the truth behind SOLDIER, Zack decided to turn against Shinra together with Cloud Strife, who becomes one of Zack's closest friends along with his mentor, Angeal Hewley, the original owner of the Buster Sword and his love interest Aerith Gainsborough. He eventually is about to die due to Shinra's army after a long and exhausting battle. When Cloud finds Zack dying in front of Midgar, he gives Cloud the Buster Sword with his last smile. A white feather representing the spirit of his mentor Angeal then descends from the sky and Zack wonders whether he has become a real hero.

He also played a minor role in Final Fantasy VII: Advent Children Complete, where he tells Cloud not to give up during his battle with Sephiroth. He and Aerith are also less directly significant through the rest of the film, as Cloud still has lingering feelings of guilt regarding their deaths. He is then seen again at the end of the movie in the church in the slums of Midgar together with Aerith.

Trivia

 * Zack asks Aqua out on a date with the line "Hey, how about one date?", which is the same line he uses to ask Aerith in Crisis Core -Final Fantasy VII-.
 * 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 (and Final Fantasy VII: Advent Children Complete).
 * Throughout Kingdom Hearts Birth by Sleep, Zack can be seen doing squats, a well known hobby of his in Crisis Core -Final Fantasy VII-.
 * Zack's theme in Kingdom Hearts Birth by Sleep, A Date With Fate, is an upbeat and brass-heavy version of Successor, from Crisis Core -Final Fantasy VII-.
 * Although Zack's first official appearance was in the North American, PAL, and International versions of Final Fantasy VII, the Reports in Kingdom Hearts Birth by Sleep list his origin as Crisis Core -Final Fantasy VII-.
 * Zack's journal entry states he looks up to Terra as a hero, mirroring how he looks up to Sephiroth as a hero in Crisis Core: -Final Fantasy VII-.