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Kog'Maw Build Guide by Deadeye Rolf

Not Updated For Current Season

This guide has not yet been updated for the current season. Please keep this in mind while reading. You can see the most recently updated guides on the browse guides page.

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League of Legends Build Guide Author Deadeye Rolf

Corrosive Agent K

Deadeye Rolf Last updated on November 9, 2011
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ADC Role
Ranked #27 in
ADC Role
Win 49%
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Ability Sequence

Ability Key Q
Ability Key W
Ability Key E
Ability Key R

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.


Brute Force
Improved Rally

Offense: 21

Strength of Spirit
Veteran's Scars

Defense: 0

Expanded Mind
Blink of an Eye
Mystical Vision
Presence of the Master

Utility: 9

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Kog'Maw: Corrosive Agent K

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.

Comments: Still in progress of finishing

7-11-11: Guide created!

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Pros and Cons

Knowing the pros and cons of your champion is by far one of the most important parts of successfully using a champion in LoL. Please learn and learn well what Kog can and can't do!

Fares very well against most current top-lane champions early game
Is flexible - can change and be successful in any of the three lanes or different builds
The longest range in LoL for any DPS carry
VERY anti-metagame
Absolutely shreds squishies and tanks alike
Even after death, can deal an AOE burst of damage to targets

Easily focused without a solid team formation into team fights
Will die if hit with early CC
VERY squishy until some health and mr is picked up, where he becomes only SLIGHTLY less squishy
Did I mention he's squishy?
Madred's Bloodrazor and Bio-Arcane Barrage do not proc spell vamp :(

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Why Flat Magic Penetration?

The items listed all focus on flatly reducing magic penetration to targets. Malady, Abyssal Mask, Caustic Spittle, and Archaic Knowledge give a TON of magic resist reduction. 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:

Caustic Spittle = 5/10/15/20/25
Malady = 6/12/18/24
Abyssal Mask = 20
Total: 69

Okay, so that is a frickton of magic resist to eat away! That Ashe with 30 Magic Resist? Here's some fun:

2 - (100 / [100 - (30 - 69)]) = 1.28

That is the multiplier of the magic damage you will deal to that Ashe. In other words, instead of your W + Madreds dealing 8.25% of her health per attack, you are dealing 14% of her health instead! After Madred's Bloodrazor + Malady, your attack speed closes in on 2 attacks per second. This means each second, Ashe is losing 28% 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. They deal absolutely monsterous amounts of damage after mr reductions.

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 ~24% damage per second to the most popular champions in LoL today! These include Nasus, Renekton, Garen, Jarvan IV, 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.

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The runes are focused on attack speed. Magic pen runes might sound like a good idea but magic penetration does NOT allow resistance to fall below zero. Pen runes will ONLY activate if the opponent has more magic resist than your flat magic resist reduction, and even then will allow for no more than true damage. Of course, this is by no means bad, but attack speed is a safer option that will activate in all cases. Greater Quintessence of Movement Speed is a strong alternative in the Quint spot since there is no kind of movement bonus items in the main build, and will allow more ease in kiting and hitting your ultimate on a fleeing target.

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Masteries are pretty basic - they focus on the offensive tree since you want to be doing as much damage as possible. That 4% extra damage is added as true damage on your magic stacks also! Offensive Mastery and Brute Force help you farm early game, and having some extra buff duration from Utility Mastery can help you keep that red buff for longer. (Or blue buff if you want to pretty much perma-ult :) ).

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'Core' Items

These are the four items that should be build every game with this type of Kog'Maw. They add up to be a total of 9195 gold, which is a very feasible amount for any game you will play in.

Berserker's Greaves add attack speed which of course increases your damage output! Don't use Sorcerer's Shoes - they give magic penetration which is much different than magic resistance reduction!


Abyssal Mask

Madred's Bloodrazor

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'Luxury' Items

The build items are chosen pretty purposefully. The total cost of this item build falls right around 14.5k gold (really cheap!) but there are some other options if you'd like! I'd generally replace Abyssal Mask with them, or late-game sell Haunting Guise to pick up a cooler counterpart.

Rylai's Crystal Scepter

Hextech Gunblade

Will of the Ancients is an alternative to build your Hextech Revolver into. It gives more spell vamp and more AP, as well as a nice aura for any AP-heavy team. Definitely an option over Hextech Gunblade in certain situations. Sadly, you DO NOT spell vamp from the Madred's Bloodrazor and Bio-Arcane Barrage procs.

Void Staff combined with Archaic Knowledge will really help anybody foolhardy enough to try and build more Magic Resist to counter you, and easily knock even 150+ Magic Resist foes into the negatives. It also gives a hefty AP boost to boot.

Wit's End is a good item that can pretty much cap your attack speed and increase your magic resist at the same time. Magic Resist is more helpful on Kog'Maw because it is generally the casters that will reach you with spells, while melee foes can be kited all day long.

Nashor's Tooth also caps your attack speed while giving CDR to all of your spells. After the recent nerf to Kog'Maw where the length of Bio-Arcane Barrage was shortened, CDR really can help out Kog a lot. Mana Regen is always helpful too.

Guinsoo's Rageblade gives more on-hit procs for hefty AP and Attack Speed boost. Strong item, but I generally see the main build choices as stronger.

Rabadon's Deathcap adds a lot of power to his spells! ...but that's about it. Go for it if you feel like you aren't hitting hard enough I guess.

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Summoner Spells

I go with Flash for the general utility both offensively and defensively to hop over walls and such. Exhaust is for that troublesome AD carry that actually makes it to you, so you can just exhaust and focus where the focus needs to be.

Ghost is by no means a bad option either, seeing as I run no Phantom Dancer, Lich Bane, or Force of Nature on this build. Make sure to take the mastery point though!

Teleport can set up a backdoor or get you to a teamfight quicker, or back from a death in lane. Again, make sure to take the mastery point.

Ignite is also cool for finishing off kills, but when you have Living Artillery that's good at that anyways, why Ignite? Same falls for Clairvoyance.

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Kog'Maw is a really enjoyable champion to play for me, so I felt like I should share how I build him! Rate and critique, comment, and enjoy!