Final Fantasy Tactics Walkthrough

This battle is pretty easy if you simply focus on Zalera. Meliadoul will mostly hide in the corner and distract all the skeletons - which, why are they here in this crypt for humans? - and the Knights won't do much; if they get in the way, just throw Phoenix Downs at them and move on. Zalera is mightily weak to Holy just as prior Lucavi, so bring along your party member(s) who can cast it.

Predictably, it also doesn't like Divine Ruination, so Orlandeau and Agrias are handy in that regard. Bring along healers because he can get angry and deal significant damage, but if you have people constantly attacking, particularly from range given the tight space and myriad obstacles, he won't last long and will finally give in. Finally, you're through with Elmdore and whatever sort of evil bug he turned out to be.

The aftermath of this battle is fairly predictable by this point of the story, though there is a cutaway scene after the main post-battle dialogue that is a bit unexpected. Turn your spoilers visible to learn more.