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Magic Penetration. Break it down!

Rudeboymike

Senior Member

Whats the AP ratio on Chicken? And I don't think Pineapple scales linearly. Definitely has diminishing returns.

wildfire393

Senior Member

Quote:
Patyrn:
How much damage do you gain from x amount of magic penetration? I can't figure out how to math it.

This is a complicated question. There is not a 1:1 ratio, because it scales depending on how much damage you do, how much MR they have, and how much MPen you have.

Additionally, there are three kinds of Magic Penetration. First, there is Magic Resistance Reduction, as applied by things like Abyssal Scepter, Fiddlesticks' Passive Aura, Soraka's Starcall, etc. This is applied before anything else and can take the target's MR into the negative.
Second is % magic penetration, as provided by Void Staff and the Archaic Knowledge mastery. As this implies, it reduces the Magic Resistance by a percentage of what it currently is.
Thirdly is flat Magic Penetration, as provided by Haunting Guise, Sorceror's Boots, etc. After MRReduction and %MPen, this applies, but bottoms out at zero.

So if your spell would deal 100 damage normally and the target has 100 MR, your normal output of damage is 50. A single point of MPen would bring that to 50.25. 20 points of MPen brings that to 55.56. 40 points of MPen brings it to 62.5. Changing the damage or MR also changes how much per point you get.

Rudeboymike

Senior Member

huh. i always thought the percentage magic pen came first. Then came MR reduction. Followed by flat magic pen.

wildfire393

Senior Member

Quote:
Rudeboymike:
huh. i always thought the percentage magic pen came first. Then came MR reduction. Followed by flat magic pen.

No, MR Reduction applies before anything, because it actually modifies the stat, while Penetration is basically "ignoring" the stat. You have to know the end stat value before you know how much you can ignore.

Rudeboymike

Senior Member

Ah ok, that makes a bit more sense. Thanks.

So runes are factored last?

ALCie

Senior Member

Quote:
wildfire393:
No, MR Reduction applies before anything, because it actually modifies the stat, while Penetration is basically "ignoring" the stat. You have to know the end stat value before you know how much you can ignore.

This is true, and this makes magic penetration less effective. If you can get them to 0 or below magic resist, any form of magic penetration is useless. Of course, it's much harder to get -MR than it is for the ally to get +MR, so it rarely happens and the only characters that can attempt it are Fiddle, Ryze and Amumu. Soraka would help, but probably wouldnt get Abyssal Staff.

When your enemies get higher MR and its pretty much impossible to get them into the negatives is when magic penetration becomes useful.

EDIT: Yea Runes would be last because they are +magic pen.

1) -MR 2) %magic pen 3) +magic pen

Unfortunately there are not enough items in each. +magic pen is easiest though (Runes, Boots, Haunting, etc.)

wildfire393

Senior Member

If you stack between them, however, you can easily ignore over 130 MR on any character, more if it's a character with -MR (amumu, soraka, evelyn, ryze, fiddlesticks, at least one other that I'm forgetting).

Abyssal takes 20 off the top, 110 remains
Void staff + Archaic Knowledge takes 55% off, 49.5 remains
Sorc Boots + Haunting Guise + 10 MPen from runes takes 50 off, 0 remains.

Rudeboymike

Senior Member

Ok, so my typical lane partner is Amumu and im a Fiddlesticks (gogo AOE comp). I am the typical Magic Pen build with Void Staff as my only Magic Pen item. He is Sunfire Cape stacking and he buys the Abyssal Scepter.

Would this be overkill on Magic Pen?

1. -50 MR (-70 at 18)
2. 40% Void Staff (when im level 30, the 15% from mastery)
3. +12 Magic Pen Runes

My questions:

Is the Void Staff necessary or overkill from most games? The reason i ask is because with that much MR reduction, its utility is diminished. Granted on a team stacking MR, ill get it.. but most games, yes or no? Mejai's would be my alternate.

Should i maximize my Glyph Runes to take advantage of the Primary AP runes or continue with Magic Pen?

Rudeboymike

Senior Member

bump