Final Fantasy Tactics Walkthrough

Give everyone Japa Mala in this battle. There are two things to do in this battle, but only one of them is mandatory, and that's killing Elmdore. The second is another opportunity to learn Ultima, and while Elmdore being there and causing problems changes the risk of learning it, it also creates some opportunity to learn it more efficiently.

If you missed it in the last battle or want to try it here, you'll want to kill Celia and Lettie immediately. In this battle, instead of teleporting away, they will transform into Ultima Demons. This will allow them to still cast Ultima but they'll lose access to all of the nasty debuff attacks they had while posing as humans. Next, run around and heal your people from Elmdore's attacks until one of the Ultima Demons starts charging Ultima. Elmdore won't be able to convert your characters to Vampire status if they all have Japa Mala, so Ramza (and anyone else with the accessory, of course) will be immune to losing control, leaving Elmdore able only to drain HP and use his Samurai sword skills.

Move Ramza into range of Ultima if necessary, and when the demons cast it on him, he'll learn it. It's much easier said than done, due to Elmdore's power, which is another reason to think again about going back and trying it in the previous battle.

To finish up the battle, hit Elmdore with everything you've got, like Holy, Jump, Samurai skills, Shockwave. Of course, make sure you have people who can heal. This battle could require a couple of tries if you want to maximize it, but if you can keep Elmdore from converting your entire party and keep them well healed from his other attacks, you should be able to stretch the battle out as long as you need to.

All of this becomes a little more moot if you just don't want to do the extra bits of this battle. In that case, skip most everything above and go after Elmdore with everything you have; your debuff-preventing accessories and healers should allow you to bear the brunt of the damage to go all-in at the start and grind it out.