Spoilers Ahead, read at your own risk.
“Don’t you have any ‘justice’, Brother!? The Beoulve name is only for the brave! You aren’t worthy of it, Brother!”
A Holy Knight of Eagrose, Zalbaag is Barbaneth’s second son. A pure-hearted warrior, he leads the Order of the Northern Sky. Even when faced with the horrific treachery of his brother Dycedarg(which he naively refuses to believe until confronted with concrete evidence), he upholds truth and goodness.
“The Savior of Ivalice”
“Lord Commander of the Northern Sky”
Zalbaag is your typical Military Personnel following orders with precision, not letting anything get in his way. He goes as far as ordering Algus (Argath) to kill Tietra. This is pretty much what we see early in the game, thus making us think that Zalbaag is the enemy. At least through the players eyes.
Later on Zalbaag learns that his brother Dycedarg killed their Father. And shortly after finding out, Dycdarg kills Zalbaag as well. Zalbaag then is called back from the dead by Folmarv Tengille to defeat Ramza, but Ramza is the hero of Final Fantasy Tactics, and thus Zalbaag perishes once more, putting an end to his story.
As I remember, I didn’t like Zalbaag in the beginning, I always thought he would turn into one of the Lucavi. I can’t even remember if he even held a Zodiac Stone.