Kog'Maw Build Guide by
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Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Corrosive Agent K: Magic Pen Kog'Maw
Most of us already knew Kog'Maw was pretty anti-metagame, correct? He deals a percent of a target's health each auto-attack, caustically corroding his way through the atmogs metagame. This build focuses on exploiting his unique auto-attacking prowess to the fullest by making opponents take as much damage as possible from each auto attack, while still melting tanks like the powerful cleaning agents under your kitchen sink.
I'm not going to go in-depth on how to play Kog because quite frankly I don't have the time, but I want to get the item set out there so we can take full advantage of his cool skill set!
Why Flat MPen?
The items listed all focus on flatly reducing magic penetration to targets. [Malady], [Haunting Guise], [Abyssal Scepter], [Caustic Spittle], and the rune page give a TON of magic penetration. Isn't that a waste?
No! Did you know that an opponents magic resistance can go NEGATIVE? Yes, you can actually increase the amount of damage you do to a target by shredding their mr to less than zero. Keeping this in mind, here is a list of how much magic pen you will have on a target:
[Greater Mark of Insight] = 8.55
[Greater Glyph of Insight] = 5.13
[Greater Quintessence of Insight] = 5.67
[Caustic Spittle] = 5/10/15/20/25
[Sorcerer's Shoes] = 20
[Malady] = 6/12/18/24
[Haunting Guise] = 20
[Abyssal Scepter] = 20
GRAND TOTAL: 122.68 Magic Resistance taken off of a single focused target.
Okay, so that is a frickton of magic resist. Remember that Singed who built the Force of Nature early game that knocks down your W to only do 3% of his health? You've just negated everything he's built. That Ashe with 30 Magic Resist? Here's some fun:
2 - (100 / [100 - (30 - 122.68)]) = 1.481
That is the multiplier of the magic damage you will deal to that Ashe. In other words, instead of your W + Madreds dealing 11% of her health per attack, you are dealing 16.3% of her health instead! After Madreds + Malady, your attack speed closes in on 2 attacks per second. This means each second, Ashe is losing 32.6% of her health, JUST from auto attacks. Don't forget to factor in that your R and E also proc from the magic pen, which can mean your other spells deal absolute boatloads of damage each second. Shredding "off-tanks" becomes even easier also: most neglect their magic resist for a large part of the game after only their Mercs, which means you deal ~13% damage per second to the most popular champions in LoL today! These include Nasus, Renekton, Garen, Jarvan, Irelia, Gangplank, Lee Sin, and Udyr. This also serves to make Agent K a great top-lane threat, where he can out-range and out-damage basically every top lane out there, keeping them from their precious farm that they need to pick up their [Trinity Force].