Gamer Corner Guides

The Dia Spells all do decent damage to all Undead Monsters, and no damage to anyone else. Because they are so limited, they generally do a lot of damage—Dia1 does as much damage as Ice1, a level 2 Black Magic Spell, but does it to multiple targets at level 1. Don't believe the bestiary when it tells you Undead are "Weak" to Dia Spells, though—this just means they're affected by them at all. Dia's damage is actually non-elemental, which means no Undead is weak to it, but no Undead resists it, either.

Dia2 is a nice Spell against Undead, almost as powerful as Fire2. Either Spell will clear out most hordes of Undead quite nicely. The only problem with Dia2, as with all Dia Spells, is that it shares a Spell level with the Cure Spells, so you may not want to cast it too much. Dia2 is usually worth it, though, especially considering the relatively minor healing of Cure2 and Heal1. As with all the Dia Spells, only a White Mage can cast it, though late in the game you will find not one but two Light Axes that let anyone cast Dia2 for free.

Dia3 is a powerful Undead killer, and it is available shortly before the Undead-filled Terra Cavern. It is a very powerful Spell, but unfortunately shares its level with the Life1 Spell. Don't waste all your level 5 Spell slots killing Undead, but don't be afraid to use Dia3 in a pinch.