every +1 INT will boost 5% of spell effectiveness. the successful rate of the spell and damage if there's any. so higher INT will increase lighting bolt's stun chance and air damage.
I don't see there's any cap for such boost, or I never get to high enough INT (merely around 21-22 range) to see the cap~
I have my INT up to 39 now, that's the best I can muster so far
. My spells seem to be pretty effective.
