Penetration

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Laiun

Senior Member

03-19-2010

Is it possible to produce negative armor if its magic or armor reduction? Say your items in game equate to your opponent having -10 armor would that give you bonus damage or is there a set reduction to zero or whatnot.?


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wildfire393

Senior Member

03-19-2010

Armor REDUCTION can indeed reduce armor below zero. The items that apply armor reduction are Black Cleaver and Stark's Fervor. It is also applied by a number of abilities, such as Puncturing Taunt, Mocking Shout, Ravage, Wall of Pain, Gatling Gun, etc.

Armor Penetration (Desolation Runes, Last Whisper, Sunder Mastery, Brutalizer) however, cannot go into the negatives, and it is applied after Reduction is (with Last Whisper being applied first)


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EnderA

Senior Member

03-19-2010

Penetration and reduction are two different things. It works like this:

1) First, reduction reduces their armor/magic resistance by the amount it describes. 5 stacks of Black Cleaver's reduction on them reduces their armor by 60.

2) Next, when you do damage to them, it incorporates your % penetration. With a Last Whisper, you're penetrating 40% of their armor. So if they had 160 to begin with, and you had 5 stacks of Black Cleaver's reduction on them, you are now doing physical damage to them as if they had (160 - 60) * .6 = 60 armor.

3) Finally, it incorporates your flat penetration. With a Brutalizer, you get 15 armor penetration. So now you're doing physical damage to a target with 160 armor as though they had: (160 - 60) * .6 - 15 = 45 armor.

You can reduce their armor/magic resistance below 0, but you cannot penetrate below 0 armor/magic resistance.

So penetration and reduction stack. (The same goes for Magic Penetration.) The only two that stack poorly are reduction and % penetration, whereas reduction and flat penetration stack well, and % penetration and flat penetration stack well. So you probably shouldn't get both Black Cleaver and Last Whisper in the same build.

For the math:

Damage after armor = Damage * (100 / (100 + (Armor - Armor Reduction) * (1 - %Penetration) - Flat Penetration)

And if reduction brings it below 0:

Damage after armor = Damage * (100 + (amount below 0)) / 100

So if they had -100 armor after reduction, they would take 2x damage, and if they had 100 armor after all penetration, they would take half damage.


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GuyGin

Senior Member

03-19-2010

I think the idea is that reduction (Starks, Black Cleaver, Haunting Visage, Abyssal Scepter) can alone bring them below zero, but the other ones cant.

So basicaly if they have more than 40 (or 56 with Fiddlestix) magic armor, you aren't going to get them below zero. If they have more than 80 physical armor, you aren't going to get them below zero. (that's in the absence of other armor reducing skills)

Excuse me if I've forgotten any of the armor redux items, I think that's all of them though.


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wildfire393

Senior Member

03-19-2010

Quote:
Originally Posted by GuyGin View Post
I think the idea is that reduction (Starks, Black Cleaver, Haunting Visage, Abyssal Scepter) can alone bring them below zero, but the other ones cant.

So basicaly if they have more than 40 (or 56 with Fiddlestix) magic armor, you aren't going to get them below zero. If they have more than 80 physical armor, you aren't going to get them below zero. (that's in the absence of other armor reducing skills)

Excuse me if I've forgotten any of the armor redux items, I think that's all of them though.
Visage is Penetration, not armor. Abyssal, Stark's, and Cleaver are the only reduction items.

You're only likely to get them below zero if you have an ability that applies reduction.


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xrats

Senior Member

03-19-2010

Interesting post.So,i wonder.Lets say i go for IE first item.What would be best for my second item?

I suppose black cleaver if most of my targets are low armor(since armor penetration and armor reduction stuck,supposing i start with full armor pen runes) or

Last Whisper if i have to deal with tanks with tons of armor.

I could also add the Sword of Divine in both cases since it deals more armor penetration and no dodge for enemies once its activated.

What do you think of this?