User blog comment:Sirhciel/Magnum - The Unstoppable Flux/@comment-12443575-20140622190952/@comment-7709681-20140622193825

Actually 10 seconds (Or are you refering to Q, because E fits better to the comparison), in this case doesn't decrease Attack Speed, but the damage reduction is too high by itself, and to make it more ridicule scales with AP which, at its best, can reduce the damage output by 80% (Compared to Exhaust's 50% damage reduction).