So you want to fight against the undead? Most people would find either a Holy Knight or a priest of Holy Light to assist them as they were, after all, mortal enemies with the undead. Many abilities and Divine Arts of these two job classes were directly anti-undead in nature, and their specialized undead detection Divine Arts would prove very helpful.
"No undead shall ever escape the judgement of the Holy Light!" The Holy Light job class members were forever confident in this saying of theirs.
Yet, in my opinion, their ability to detect the undead wasn't as great as it seemed on the surface. It worked behind the principle of Holy Light's natural undead magic resistance. They would release a minute amount of Holy Light into their surroundings and consequently hunt for instances of resistance.
