thats why there says "i can beat any tank"
they ll be allways at 0 magic resist and you could do extra damage
thx for reading

With the amount of magic penetration and reduction you have, void staff will do almost nothing except against galio. % pen is calculated last, and you reduce/pen through over 80 without void staff, so on most enemies, you have had them at 0 MR for about 10 levels. (pen won't make them negative).