How does Magic pen work?

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CamaHa

Senior Member

12-07-2013

Quote:
Originally Posted by Scooter Sparkle View Post
Void Staff negates 40% of their total magic resist.
Psst it's 35% since changes to pen calculation.

OP: it's easy. Imagine opponent got X MR.

if u have void staff (35% mag pen) then dmg is calculated as if opponent has (X-X*.35) MR
If u have Haunting Guise (15 flat mag pen) then dmg is calculated as if opponent has (X-15) MR
If u have both then dmg is calculated as if opponent has (X-X*.35-15) MR

% mag pen is applied before flat pen (Total MR). Old formula (let's keep void staff at 35% for easier comparison) was: (X-(X-15)*.35 -15) MR for the case with void + haunting.


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alaskaneagle

Senior Member

12-07-2013

54367

They changed the way Pen works last season. Now the % is taken first and the flat is after SO; if you get the 12% in mast's (if you are an apc you always should) and you get void staff it's 52% and you jsut cut their Res's in half. Cool more dmg.

Now what I do is build up AP early game to make them Want MR. I'll shy away from Pen at first only picking up the boots (though sometimes I'll get the ionian boots to bluff them into thinking I won't buy MagPen). Then after I am scary enough that all the enemies are building MR I buy; MagPen boots, void staff, and either liandry's and/or abysal scepter (depends on if I have a slow, dots, and/or other ap's on team) Now I have 30 flat and 41% so if they have merc treads and a spirit visage which is 80MR they will instead have about 15. If they are picking up a third MR item I will definitly get both liandry's and abysal since a third will usually bring it up to 120 or less which means they will still only have about 15 MR.

Basically if you rush a deathfire they will rush MR and you can buy pen boots, laindry's, void staff, and abysal scepter without really sacrificing any dmg stat's. So you'll melt tanks and carries alike, and still have room/gold for another item since this build isn't overly expensive compared to fighting against it. (if you get all these items and they only build one negatron item and merc treads you'll be doing true dmg as if they had 0 MR even though they spent 4k+)

O and extra bonus; they are nerfing rammus so he won't be able to stop you from nuking him to death.


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Mynt

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Senior Member

12-07-2013

The Mage's negative emotions manifest in a physical way, producing sharp spikes in their usual energy wave forms. These spikes have a high peak of angular momentum at the point of impact, partially negating any magical resistance they come against. Furthermore, this action is passive, requiring no additional sources of energy after the initial morphing has occurred.


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March of Dimes

Senior Member

12-07-2013

Quote:
Originally Posted by Tesla23 View Post
they work like this:


tank spends +10k on tanky stats.

squishy gets a single 3k item.

Tank now has no stats
...and this little piggy cried allll the way home.

Seriously though, just stack health against casters. They either blow their DFG proc on a health stacker, or they build liandry's - either way they deal less damage to your damage-dealers.


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Laain

Senior Member

12-07-2013

What if your magic pen exceeds their magic resist?


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Khristophoros

The Council

12-07-2013

Quote:
Originally Posted by Laain View Post
What if your magic pen exceeds their magic resist?
Then they have 0 MR against your damage. It doesn't go negative.


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March of Dimes

Senior Member

12-07-2013

Quote:
Originally Posted by Laain View Post
What if your magic pen exceeds their magic resist?
The extra magic pen is wasted - you'll only take them to 0 MR. Technically, a combination of debuffs greater than their MR will take them negative, but that's extremely rare to see.


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Biggg O

Senior Member

12-07-2013

So if someone had 100 mr and you had void staff and haunting guise, no runes/masteries. You would do
100 * .35 - 15 = 50 mr


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Registeel1234

Recruiter

12-07-2013

First, you need to understand how defenses work. Magic resist reduce the damage taken by a percentage. The formula is this : MR/MR+100

So, for exemple, if you have 100 MR, you get 50% reduce magic dmg (100/200 = 0.5)



%MRPen reduce the MR first. So let's say you got void staff (35% MRPen) and that your enemy has 100 MR. You reduce that MR by 35%. So your enemy get 65 MR after your MRPen (100 - 35 = 65)

But if you also have flat MRPen, you remove a flat amount of MR after the %MRPen. So if you also have sorcerer's, your enemy get 50 MR after voidstaff and sorcerer's (65 - 15 = 50)


After MRPen, the game reduce the MR from debuffs and items (Dread, starcall, ect...). Again, it reduces MR by a flat amount.


So the order is : %Pen - FlatPen - DefenseReduce


I't the same thing for Armor




EDIT :

Quote:
Originally Posted by Khristophoros View Post
Then they have 0 MR against your damage. It doesn't go negative.
Yes, it's true, MRPen cannot make you more dmg than normal. However, defense reduce, like starcall can make you deal more dmg than supposed to.


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Phreak

Shoutcaster

12-07-2013
1 of 2 Riot Posts

You're asking for some math as well, so here goes:

First, % penetration works first. So if I have a Void Staff/Last Whisper, I pretend your MR/Armor is only 65% of what it really is. Then I factor in things like Brutalizer/Sorc Shoes/Haunting Guise. Those things work additively. So for example, if you had 200 MR and I had Void/Sorc/Haunting, Void reduces 200 to 130, then Sorc/Haunting reduce that 130 to 100.

So instead of dealing 1/3 damage (fighting 200 MR) you deal 1/2 damage (fighting 100 MR). Thus, the passives result in you dealing 50% more damage than before.

Note that penetration can only go so far. What I mean is that, if you have exactly 100 flat magic pen, it will only give you at most 100% bonus damage (your opponent has 100 MR). If your opponents have any more or less than 100 magic resist, you will get slightly lower returns.

Example: You have 100 MR, so I deal half damage. With 100 magic pen, I deal full damage, aka double what I would have before. If you have 200 MR, I deal 1/3 damage. I reduce that with my 100 magic pen to 100 MR, and I now deal 1/2 damage, so 50% more than before. If you have 50 MR, I deal 2/3 damage. With 100 magic pen, I deal full damage, or 50% more than before.

I hope those all made sense.

Quote:
Originally Posted by Tesla23 View Post
they work like this:


tank spends +10k on tanky stats.

squishy gets a single 3k item.

Tank now has no stats
Mathematically this isn't true; they roughly equal out. If you had 80 base armor and bought Thornmail, and I bought Last Whisper, your armor went from 80 to 180, then I reduced it to 117. Obviously we each got some extra stats (damage return, 40 AD), but it's pretty easy to see that while % pen is useful, it does not completely devastate tank items.