.65 * .6 * .9 = .351, so 1-.351 = .649, or %65 penetration.

Magic Pen. percentage stacks multiplicatively. Not sure about the exact nubmer, but it's not 85%.

I like your guide as Xerath is a heavy damage dealer Void Staff is ok for me but NinjaGinge said calculation is not that simple.

First comes passive like Abyssal Mask then comes Flat penetration like runes and Sorcerer's Shoes. Then comes % penetration as Void Staff but adding % penetration is not that simple. Max % penetration is %49. Like %40max CDR. If you check it ingame when you have Void Staff and Arcane Knowledge you will see your magic pen is (flat)/%49

Ex= Enemy guy has 149 M.res.
1st comes Abyssal Mask => 149-20 = 129 this is the new magic resist of enemy when your near

2nd comes Sorcerer's Shoes(20) and Greater Mark of Magic Penetration (approx 9) => 129-29=100 Mean when you hit a magic damage you will deal damage like he has 100M.Res

If you have Void Staff + Arcane Knowledge you will penetrate the REMAINING M.Res from this far. 100*%49=49M.Res you penetrate more. 51Remained.

If an ally hits this target with Malady ofc reduced amont will be taken in 1st step. Its not a penetration is a global decrease for every ally


But overall good job but please change it as soon as possible. Im voting +1 but again please make your update :)

1) no if you are sniping then the passive aura will NOT be affecting their team and it does not apply a buff to your team

2) That is NOT how it works

3) idk how mana issues come into play forming an opinion on this item

4) your math is way off. %penetration does not stack additively so you do not get 85% penetration. And you will hardly ever get the aura from Abyssal Mask so unless you have a death wish by getting that close you don't have 48 flat pen either. you get 28.

1. your teammates are still going to get that Abyssal Mask buff if you're sniping their team, but if you aren't in locus of power and running into a fight, then yes you will have Abyssal Mask up on their team and your's.

2. for all i know there is no cap to MR shread. just like there is no cap below 100% that i know of for lifesteal/spellvamp. best case scenario is that the game does percentage spell pen then the flat shred and not flat shred then percentage.

3. i've never had mana problems with Xerath so it's not an type of item i'm really concerned about. being the ap carry on your team, you should have priority over blue, unless your team is stupid or jungler is a ******.

bingo

Imho abyssal scepter is totally wasted on Xerath.. Because when you close enough to let the passive kick in you are doing something wrong ;)

good looking guide, seems to be viable.

would like to see some game play sections though

Nice guide. Add some more gameplay-related stuff to the guide, as prospective Xeraths would need it.

% magic pen and flat magic pen dosen't work so well together. and I believe your math is wrong. Lets say they have 100 MR. MR recution comes first, so they are a 80, -28.55 ( 29 then) they got 59. With your 80% magic pen ( 40% VS, 30 LoP and 10% ,mastery) they are at 9.6 ( 10). There also might be a soft cap to % Mpen. I'd suggest changing your seals and glyphs to something like mp/5 or Mresist and changing WotA to a mana item like archangel staff or something.

Anyway nice guide, but maybe a little short.