"While equipped with a Wand or Staff, replace normal attacks with Holy Arrow attacks that inflicts X% of normal damage."
Holy Arrow is an extremely powerful attack for Priests and Arch Mages. It allows you normal attack to become significantly more powerful. Beginners are advised to add points to this skill, as it allows ranged use of the normal attack, as well as being more powerful. Normaly You just need to put a point in this skill.