Zack is a Vestal boy with a silent tone. He is the eldest and most mysterious member of the brawlers. His background is still not yet explored as he has been absent in the first half of season 1 and season 2. However, Zack is known for the many battles he has won. He is silent, most of the time, and is mature. He often acts as the voice of reason within the Brawlers, which is why the others refer to him as being the "big brother" of the team. He is also quite wise and would often give helpful tips and advice in brawling to his fellow teammates.
Zack has a habit of arriving or appearing in battlefields out of nowhere while others do not know how he gets there. He seldom smiles and rarely shows any emotion.
Zack is the master of Darkus Bakugan. His words for choosing this element is this: "Darkness is silent, swift and endless, but can be sinister and cruel. I feel it as a lone shadow with only itself to rely on, though it is willing to help and depend on others. My unknown abilities to those who wish to understand is my key to victory. I am Zack Yosaki, the shrouded Darkus Brawler.
- Darkus Crelune: Guardian Bakugan
- Darkus Were Crelune: Evolved prior during repeated battles
- Darkus Moon Crelune: Further evolved after passing Excedra's test.
- Darkus Hyenoid
- Darkus Siege
- Darkus Centipoid
- Darkus Warius
- Darkus Mantris
- Darkus Falconeer
- Darkus Dracina: Guardian Bakugan
- Darkus Necro Dracina: Evolved prior to their arrival.
- Darkus Eclipse Dracina: Further evolved after receiving the Darkus energy from Excedra.
- Darkus Moon Crelune
- Darkus Batshade: Bakugan Trap
- Darkus Gheizt: Guardian Bakugan
- Paraclaw: Battle Gear
- Darkus Bandmumra: Guardian Bakugan
- Mechtogan Midnights
- Mechtogan Titan Midnights
- Darkus Shadestein: Guardian Bakugan
- Darkus Bandmumra: Second Guardian Bakugan
- Mechtogan Eclipso
- Darkus Abyssea: Shadestein and Bandmumra Fusion
- Zack is the oldest and most mature of the brawlers.
- Because of his absence in the first half of Battle Brawlers and New Vestroia, he is among one the most mysterious characters in the series.
- Since his debut, Zack has teamed with a Darkus brawler of each season and strangely enough most of his partners turned out to be the enemies of the brawlers; Alice was Mascarade who was originally the enemy of the brawlers, and Ren who at first deceived the brawlers into thinking the Neathians were their enemies. Ace was never an enemy to them.
- His Bakugan are based on dark or folklore creatures.
Opponents & OutcomesEdit
- Many Random Brawlers - All Wins
- Masquerade - Win
- Illusionary Masquerade - Win
- Masquerade (tag w/ Ho Roshi and Dan Kuso) - Win
- Centorrior and Druman (tag w/ Ho, Dan and Nova Lion, later Masquerade) - Win
- Rabeeder (tag w/ Alice, Christopher and Klaus) - Win
- Hal-G (tag w/ the Battle Brawlers) - Win
- Mylene Farrow and Shadow Prove (tag w/ Hikaru Komane; flashback) - Win
- Mylene Farrow and Shadow Prove (tag w/ Kaza, Chima, Shun and Marucho) - Win
- Mylene Farrow (tag w/ Ace and Klaus) - Win
- Julie Makimoto and Billy Gilbert (tag w/ Ace Grit) - Win
- Shadow Prove and Lync Volan (tag w/ Chima, Ace and Marucho) - Lose (due to Trap Field)
- Hydron (tag w/ Terra and Hikaru) - Win
- Zenoheld (tag w/ the Risistance) - Win
- Dan Kuso and Ho Roshi (tag w/ Ren Krawler) - Draw
- Sid Arcale and Zenet Surrow (tag w/ Ho, Dan and Ren) - Lose