Armour/Magic Penetration/Reduction questions

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0shi

Senior Member

11-23-2010

Hey there, just trying to figure out how Armour/Magic Penetration/Reduction interact with each other.

1) I've been told that Armour/Magic Resistance cannot be reduced below zero by penetration, but can be with reduction effects (Stark's, Black Cleaver, Abyssal Staff, Fiddlesticks etc). Is this true? If so, is the below zero reverse scaling similar to the above zero defensive benefits?

2a) If (1) is true, how do penetration/reduction stack together?
A common example: I'm wearing 43 penetration from boots/haunting guise/runes, and have a -20 aura from an abyssal staff while attacking a an opponent with say, 50 resist, what resistance does he have? -13 from (50 - (43 + 20))?

2b) If (1) is false, can you simply calculate the total reduction to armour/resistance by adding together the amount of penetration + reduction you have, down to a bottom value of zero?

Cheers.


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PhailRaptor

Adjudicator

11-23-2010

1) Reduction can push a stat below 0. Penetration can't.

2a) In the following order:
% Reduction
Flat Reduction
Flat Penetration
% Penetration

So for Armor, Starks and Black Cleaver stacks would apply first, followed by Youmuu's, Sword of the Divine's active, and runes. Finally, Last Whisper would apply.

For MR, Nid's Bushwack traps would take effect first (the only source of % Reduction that I know of). Then Fiddle's passive, Abyssal Scepter, and Malady stacks. Next, Haunting Guise and Sorcerer's Shoes. Finally, Void Staff and the Archaic Knowledge mastery. Keep in mind that % penetration stacks multiplicatively, not additively. So with both Void Staff and Archaic Knowledge, you'd have 49% penetration, rather than the 55% you would get if it was straight up addition.


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0shi

Senior Member

11-23-2010

Thanks, that's a perfect explanation