Final Fantasy Tactics Walkthrough

The biggest hassle with this battle is that at the beginning, Barich poisons all of your characters. The best thing you can do is bring a Monk and gather all your characters around him and have him use Purification, which will heal them of their poison. The Monk's Chakra ability will also come in handy here, because it's free healing against the sharp-shooting Barich. Adding Angel Rings to your healers is not a terrible idea. In any event, don't rush into this battle until you are able to deal with the poison.

Barich has a Glacial Gun, which is completely overpowered for this point of the game (at least as guns go); instead of simply shooting a projectile, it shoots Blizzard magic. It usually hits with a powerful form of the first-tier cast, but it can surprise you with second- or third-tier from time to time as well for massive damage. This gun is amazing, and it's in your best interest to kill everyone else off and try to steal the gun from Barich, because it's one of the most powerful guns in the game and you won't see it again for quite a while.

The other enemies will only give you trouble because they're separated from you by the walls of the building, but a well-placed Summon will crush them. You'll want to handle the ranged attackers who are not Barich fairly quickly, especially if you want to have a run at stealing that gun. Additionally, Barich seems to prefer attacking Ramza above other units, so you can use your main character as bait to help accomplish whatever your goals are for this battle.