Zack

Zack is a character in Kingdom Hearts Birth by Sleep set to appear in Olympus Coliseum and is the only Final Fantasy character to appear in the game other than the Moogles. While his exact role remains unknown, he is shown in scans to be both a boss and D-Link for Terra. He 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.

Kingdom Hearts Birth by Sleep
Zack appears in Olympus Coliseum. Zack has been seen fighting against Terra under Hades control, used as a Dimension Link, and talking with Ven and later fighting the Unversed alongside him and Hercules. Later, he was seen asking Aqua out on a date. Aqua shakes her head and arms in embarrassment. It is because of Hades that Terra and Zack met to begin with.

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 feather drifting down where he once stood.

Fighting Style
Zack is fought twice within Terra'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 more quick. 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.

Appearance
Zack sports his original hairstyle of short, thick black spikes with bangs framing his face. His eyes are a bright blue. Likely 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.

Recent scans have also shown Zack to wear a Gladiator/Spartan style helmet in some instances.

Trivia

 * Zack is the fourth Final Fantasy character to be introduced at Olympus Coliseum (following Cloud, Sephiroth and Auron), and the seventh Final Fantasy VII character to appear in Kingdom Hearts. Because Zack has been redesigned to be in the the same style as the residents of Olympus Coliseum, its possible that it may be his home world. If that is the case, Zack would be the first Final Fantasy character whose home world be one based off a Disney movie, rather than an original Kingdom Hearts world like Traverse Town, Radiant Garden, or Twilight Town.
 * 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 the fact that he was also an apprentice at a young age under the tutelage of his former mentor Angeal 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 the movies Final Fantasy VII: Advent Children and 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.
 * Throughout Kingdom Hearts Birth by Sleep, Zack can be seen doing squats, a well known hobby of his in Final Fantasy: Crisis Core.
 * Four of Zack's battle attacks imitate attacks used by Cloud from Final Fantasy VII, including Braver, Omnislash, Meteorain, and Assault Twister. However it should be noted that Zack was chronologically the first to use such attacks as Cloud had inherited them later on.

Zack