Magic

Pick your poison:

The Girl : Specializing in healing and assistance magic, she'll keep the group alive, bring them back from the dead if that didn't work, and enchant weapons with elemental magic. If you want all your hit points back in a single spell or your weapons to stay enchanted longer, keep raising her magic levels at every chance.

The Sprite : He/it is the battlecaster, with loads of damaging elemental magic and spells that can cause negative status effects. Keeping the sprite's magic levels as high as possible goes a long way in making the game much easier.