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Mechanics Clarification with M. Pen. and Reduction

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Q: What order is armor penetration/MR penetration applied in? (Credit to TiberiusAudley)

A: From top to bottom

Armor/MR Reduction
% Based Armor/MR Penetration
Flat/Linear Armor/MR Penetration

Q: Can you reduce armor or magic resistance below 0?

A: Yes, although the only things that can reduce below 0 is Armor/MR Reduction. Both percentage and flat penetration do not have an effect after they get to 0 armor/MR.

The above is from the mechanics explanation thread.

My question is this. If reduction is applied first, and is the only way to reduce past 0...

Wouldn't it be impossible to reduce past 0?

It seems that even Fiddle's passive + Abyssal Scepter doesn't have enough potency to breach that threshold...

Help me out!

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Senior Member


Amumu's passive reduces it by 40, eve's ravage reduces it by 26, Ryzae can reduce it by 90 with good timing and some luck, exhaust reduces it by 10, and magic resistance reduction stacks with your teamates.

So if you put Amumu, Ryze, Eve, Exaust, Abyssal Scepter, Fiddle together you can get
40+90+26+12+20+16=204. You can definitely get someone below 0, its just not all that easy.

Edit: Note that multiple exhausts and abyssal scepters will not stack with themselves (aka 2 exhaust is still only 10 magic resistance reduction).

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Senior Member


Don't forget Soraka's Starcall (-8 MR/cast, stacks 20 times), or Karthus' Wall of Pain (-35 MR at lvl 5).