Ganking the Meta

Let's talk Black Cleaver, and Arm. Pen.

Yes, I know that It's nerfed now.

So, if you play Leauge regularly and have done so for the last month or so, you are probable aware of how vastly OP Black Cleaver, and armor pen in general had become, as a result of the season 3 patch. In fact, the item was so OP that it made AP champs rather useless compared to BC wielding bruisers, and actually became -the- item to build. Now, you might not have played enough to know why or maybe your dyslexic, either way, here is way. 

Black Cleaver, after the nerf, is still a good item, especially on bruisers, since it provides them with the vast majority of the stats they need: CDR, AD, Armor Pen, HP. This stat combination alone, almost without regard of amount/value is and was enough to make this a beast item for any bruiser, especially since it builds off a Brutalizer, making it easy to get fast, getting you all that early dmg to snowball your team and fulfill your role as bruiser effectively. Now, what it also did and still does, although in a slightly weaker version, is that it applied a debuff reducing the targets armor by a percentage (keep in mind that the S3 patch also introduced an update to the way penetration was calculated, meaning that % penetration is now subtracted BEFORE flat, which is immensely better than before) this debuff stacks up to 4 times, and provides a solid chunk at the fourth stack. Now, Riot has admitted the item was broken, but have thus far claimed that you could not get more than 4 stacks, even with 6 Black Cleavers, thus debunking some of the wildest rumors, saying that 1 hit with  6 Cleavers would instantly remove 100% of the enemy's armor. However, even with the debuff stack being capped at 4 regardless the amount of cleavers, more cleavers still = quicker application of the debuff; basically, if you have 4 cleavers and hit someone once, they will instantly have 4 stacks, meaning that your next attacks will deal a lot more damage.

The reason for this, was the lack of unique abilities on the item. The application of the debuff was not unique, which as explained was rather good, but neither was the CDR nor the Armor Pen. This was broken, through the roof broken. What it meant was, that a snowballing bruiser, would fairly quickly be doing true damage, to your entire team. That is insane, especially considering champs like Riven or Talon, whose abilities scale with ad and does physical damage, as well as being AOE.

Let's do the math. 

Running Riven top, Phreak has gone for full arm pen marks and flat AD quints, giving him 12 armor penetration flat. He is also running 9/21 masteries (for the sake of fairness and to avoid the glasscannon syndrome) providing him 8% armor penetration. Doing the game he gets fat and farmed all sorts of good thinks and buys 4 Black cleavers, T2 boots and a Last Whisper. This gives him the following:

40% CDR, 1K health, 240 AD, 60 flat armor penetration, 35% armor penetration and the debuff from cleaver providing an additional 30% armor penetration since it is applied instantly. Phreak smiles, since his Riven, who mind you does only physical damage, and almost only AOE, now ignores 73% of the enemies armor, and an additional 72 afterwards. 

WHAT DOES THESE NUMBERS MEAN!? 

They mean, that the bruiser who will be sitting at 300+ AD and does physical damage with ALL her abilities, (most of them doing AOE as well) will hit everyone on your team for 100% of her damage: True Damage. The only ones negating any of the slaughter will be tanks with heavy armor builds.

And that, is why Black Cleaver was broken as fudge.

NOTE 1: There is confusion as to whether or not armor pen % is capped at 40 game mechanic wise, or just on champ sheet. I believe it's the latter, due to the numbers I've seen bruisers dish out.

NOTE 2: Black Cleaver is STILL an extremely good bruiser item, even after rather tough nerfs. It still gives you an incredible set of stats.

Hope you enjoyed, and survived!