a priest has an aura, the distance the aura can go is determined by the staff(long staff has long range, battle staff short etc.) if you give you priest str it gets an aura of attack, for each str point the aura goes up with 1% each character in the aura gets (Number of str points)% attack. dex gives your priest an aura of defence, 0.2 defence per point. if you have 1 defence all dammage is reduced by 1. magic does nothing of vallue.
if you are high a lvl you could get +50% attack or more!