Despite their namesake, they are, in fact, more of a support spellcaster, and frequently show up alongside other monsters, typically Dark Wizards, but occasionally other foes. They can heal party members, buff them defensively, provide heavy magic resistance to a teammate, or dispel allied buffs.
It is recommended to target them first. Their HP is unimpressive, and their defense is mediocre, and they will go down quickly if targeted. The key is not letting them stick around, lest they make a fight far more difficult.