Talk:Kassadin/@comment-143.176.54.12-20120716103258/@comment-88.186.19.90-20120716113223

This is how void stone works: Imagine an enemy throws 200 points of magic damage at you.

You reduce the incoming damage by, let's say 25% because of your Magic Resistance. The remaining 150 damage then gets reduced by 15% because of your passive, preventing 22 points of damage. You get dealt 128 magic damage, and your attack speed increases by 22% for 4 seconds.

If the enemy throws another 200 damage spell at you 3 seconds later, then the same thing happens: you get dealt 128 magic damage, and your attack speed increases by another 22%. HOWEVER, the stacks are not cumulative over time, so you will have a total attack speed bonus of 44% (22+22) for 1 second, then the first bonus will wear out and you'll be brought back down to 22% bonus attack speed for 3 seconds before the second one expires too.

In other words, the AS boosts add up together but do not reset each other's timers, a specific AS boost from your passive will only last 4 seconds whatever happens.