This is a general AD kog maw build, with some survivability going in there as well, not the normal idea of survivability however. This build is designed for a team with strong cc and aggro pulling (away from you) and for teams that can maintain good map vision control.
Special thanks to Mowen, and others on Mobafire here as their builds were a great starting point for me with this build.
AD Build explanation
Sorry I'm not big on the whole visuals side so I'm only bothering to keep this short and sweet. I doubt anybody will be reading this anyway haha
The idea behind the build is to play bot with support or in a very strange team comp, play solo mid. I'm not going to tell people how to do this, there are better Kog'Maw game play guides out there that can give you the basics on play style and skill shot use.
I have gone for pretty typical ad start, with wriggles as a plus, to help my support and give me very early game survivability. Then grabbing some good mid game items hopefully allowing you to start racking up some kills. With your feed you can build into some expensive items that should you carry you into late game.
In late game we should be finishing off our large items with either our team winning our you being able to secure kills and your team keeping people off your back largely. Grabbing a couple of items that give you a bit of survivability (health and vamps) and slows, as we don't really want to waste time trying to tank and most teams will be coming for you anyway, going for a different type of survivability of cleanse and then applying a slow via e or r.
This build is based on your team having good ward coverage and therefor vision of the map, which will be done by your support, jungler and a little by top. This will keep you relatively safe from ganks and allow you to move through the jungle to get several hits off with your ult.
Hopefully this build will help you on your way to become a pokemon master
AD Summoner Spells
Ghost and Cleanse.
We are going for Ghost for speed, whether its from a fight or a gank, Or towards a fight that started without you or chasing an enemy. Ghost is important over flash as often you will be targeted by Assasins, who have flashes or gap closers and you need to be able to put on a lot of distance, not just one little pop that one of their moves will easily match.
Cleanse is going to be necessary when you get cc'ed in a fight and need to get back to ruining the enemy team. Don't let one cc take you out of action for 3seconds with another cc following straight after, removing you from most of a big fight, cleanse will let you attack or run as you choose and will reduce any incoming debuffs by 2/3s of duration.
Flash is good, and watching any pro game will show you that, I just think ghost/cleanse are both more important for you in this case. If you want to take it because it suits your play style better, then go for it.
Teleport is also a viable option especially as a carry who needs to be in on team fights and getting their feed as often as possible. HOWEVER as Kog'Maw only has his e as an escape mechanism I would say his summoner spells should be focused on helping him there rather than getting him even better feed than he already has. If you can handle it then take it.
Pretty typical 21-9-0
Taking points in summoners resolve and summoners wrath, given our summoner spell choices.
I'd say this is pretty much a given for a glass cannon like Kog'maw. There's the option of taking health regen and mr over health in the defense tree, however I would say kog definitely prefs the early game help over the sustain.
If you know from team comp before a game that you are going to be playing mid then take Resistance over Hardiness.
Pretty standard stuff here as well.
Only ones that I would consider changing are the quints or glyphs, but I'd say they are probably the best choice out there.
Glyphs you could go flat Mr, but thats totally up to you/your lane if you know it in advance.
Maybe Cooldown reduction/lvl, but I would say a little bit of survivability would be better given Kogs intrinsic glassyness. If you want to be able to use your W more often then they can be a great option however. Go for flat CDR if you want to get your W more often early, or go for CDR/lvl if you can wait till level 13 or don't have the mana early to use your abilities straight after they come off cooldown early on.
Go for MP5 seals and MR glyphs if you are taking Mid.
We go for a strong start with Dorans, rather than boots. Dorans will help you 1v1 early and get kills/survive while boots are better for poking.
Dorans is also better because you are starting with E and so are less likely to need to chase, if you are winning a fight.
Dorans is better for ganking at level 1.
If you are more likely to play passively early due to match up or your lane partner then go for boots and pots. We should be grabbing boots on first trip back anyways.
Mid game items are:
Berserker's Greaves and
These should give us lots of sustainable dps and keep you putting pressure on lane, maybe netting a kill or two.
Boots can be swapped for whatever situational you prefer. Playing mid you will want Merc's.
Coming out of mid game you want to grab:
Bilgewater Cutlass and
The Black Cleaver
These will give you real damage and make you into a serious force to be avoided.
As you get your feed on you want to pick up:
Rylais Crystal Scepter
Phantom Dancer and
These items are where my build severely differs from others. You are going to rely on getting a slow off to escape ganks or when you are targetted in team fights. This is done by Bilgewater cutlass or Void Ooze. Later rylais and upgrading Bilgewater into Hextech Gunblade will help with this, giving you 3 options for slows. You are also going to be relatively fast with Zeal/Phantom Dancer, boots of swiftness and your MS Quints and boots of swiftness, this is doubly useful in allowing for being able to out run enemies better and also helping you with chasing and positioning with your skillshots.
Rylai's Crystal Scepter is really great on Kog and I explain why it's worth getting on this build despite not matching up with the AD nature of it.
Hextech Gunblade will give you great sustain for someone who doesn't have another heal and gives a bunch of damage to boot. One of the best things about it is the huge 50% slow with a range increase over Bilgewater Cutlass, making it as long as your auto-attack with your Bio-Arcane Barrage up.
Upgrade your boots to Swiftness once you have a lot of AS and won't miss Berserker's and need the additional movement to get away from all the pesky Assassins coming at you. When/if you do this is up to you. In games where you have gone Merc's or Ninja Tabi it may not be a good idea to switch. I have found in the past that around the time you grab Rylais is good.
Unusual but the way I am usually able to play Kog, if you get ganked alone you are already dead and out of position so deserve to die and any little bit of health or armour isn't going to save you. If you are going to be able to escape a death then its more likely that you will be able to get away with a combination of Void Ooze, Rylais, High Movement speed from boots, quints and items, and ghost and cleanse.
If you want to go for more defensive items over the escape tactic ones I use then go for it, but I prefer to keep my glass cannons glass and not pretend they are anything else.
Rylais Crystal Scepter
Rylais Crystal Scepter is almost a must for Kog, as anybody who has played AP will know, landing a second Living artillery or being able to hit multiple targets, is a lot easier with RCS.
The importance of being able to land a few Living Artillery in succession are really good in these situations:
Landing multiple hits on multiple enemies. Being able to hit a group of enemies is a lot easier, even with only the 15% slow. Softening a few enemies can make them a little more hesitant to start a fight or make the difference in a team fight.
Harrasing a single enemy. Being able to stick with a single target with your ult while laning or just while they aren't ready for it. Even 15% slow can often be enough to put off a player. Just being able to land 3 hits (~1000 Health on any carry) before a big fight can make a huge difference.
Harassing tower huggers. Often times landing a few Living artillery and threatening them with more, is enough to drive enemy champs behind their tower, giving you range to get a handful of shots off on the tower or creeps.
Chasing. Having a slow on Living Artillery can often mean the difference between a low health enemy escape and get away. Sure you can land a few hits either way, but the slow will help you or allies finish them off. The slow will also stay on a target despite a flash or duke, making them easier to follow, through jungle etc.
Bush checking. Landing a slow can help you land another hit on a bush hider, potentially deterring them away from jumping you or giving you more time to run.
Escaping. If you see someone coming for you, a Lucky Living artillery may give you that little bit of time you need to get away or throw a Void Ooze right onto where they walk.
IN A TEAM FIGHT.
Being able to affect positioning during/before a fight with Living Artillery is an awesome part of being Kog and having the slow only adds to it. Letting your initiator get to your enemies easier by slowing them lets your team decide how to engage.
These are reasons why I usually go for Rylais on Kog'Maw. Not for the damage or the health or because it always gives me more kills, but the small ways it affects games. Maybe you don't have as many kills as if you went for more damage but it helps you in ways that win you games.
AP Build Description
The AP Builds are to be played Solo Mid, against an AP character.
The first of the AP builds focuses on getting strong repetitive pokes from your ultimate, helped as early as possible by the slow from Rylais. Focuses on getting mana and AP early, this is likely useful against enemies that are easier to harras as they have less range and less mobility like:
The second of the AP builds is more focused on last hitting early and being in (or getting away) closer quarters with enemies more often and coming out better off. Focuses early are AD
and Life Steal. This is more important against enemies who are not easily as easily harassed by R and are inclined to jump into close quarters with you. This includes champions like:
Both Builds have the same end build they just have different ways of getting there.
The builds full stats are displayed Here.
As you can see the build gives a total 834 AP as well as a 15% slow on his ultimate and Q & E.
This gives his R-tillery a crazy 613 magic damage to champions with little or no risk of them being able to counter attack (I mean who else has a range of 2200?)
He can spam this once per second giving a DPS of 613 per second less any Mr. Assuming you are correctly targeting the enemies squishes who will have no more than 60 MR you are looking at doing 472 damage per second. This will also apply your slow making it easier to land subsequent hits.
If enemies think that you are going to be an easy target and try to run out you, you are likely to be able to land a hit or hopefully two of your R-tillery slowing them. Next thing you will try is your E, This gives a slow of 52% as well as 844 magic damage if they are foolish enough to get hit by the ball of it.
Once they approach you you are most likely to have a greater range than them, with his W giving a range of 720 and procing Lich Bane.
Your subsequent attack will do base damage of 103 + lichbanes proc of 834, a total of 937 physical damage. Your W also grants a %life magic damage bonus of 6%, the bast amount + 8% from your ability power, giving 14% max life as magic damage. Based on the average assassin having around 3000 health with 100 Armour and MR (this is an overestimate, but showing you the upper range of what enemies you are likely to have charge you) you will be doing an extra 420 Magic Damage per hit.
This first hit is therefore going to do: Real Physical Damage of 937*100/(100+100) = 468
Real Magic Damage of 420*100/(100+(100-29)*0.9) = 256
A total First hit of 724.
With an attack speed of 1.165 per second and them likely being slowed in front of you, you are likely to be able to get off another 2 hits before they are in range to hit your with their abilities or in the case of ARADC an auto attack. This second hit will do: Real Physical Damage of 103 *100/(100+100) = 51
Real Magic Damage of 256
To give a total 1335 damage to quite a tanky assassin coming at you. This is almost 1/2 of their health before they can even land a hit on you, possibly more if they were hit by your R or E.
Next you are likely to to be able to get at least another two actions off without being bursted down.
Your next move will be to use Q, Caustic Spittle which slows them 35% and hits for 844 magic damage to do: Real Magic Damage of 844 *100/(100+(100-25-29)*0.9) = 597
This will also proc Lich Bane again and your next Auto Attack will do:
Real Physical Damage of 937*100/(100+100-25) = 535
Real Magic Damage of 420*100/(100+(100-25-29)*0.9) = 297
E and the subsequent autoattack will do a total of 597+535+297= 1429
In the roughly 3 seconds it has taken for your enemy assassin to move from 720 range to land one possibly two hits on you, you have done 2764 real damage to them.
Hopefully you either landed a few hits on them before they got into range of you and they are now dead or you had team mates able to fire off just one or two hits to let you finish of this enemy.
If they are still alive with less than 10% health, many players attempt an escape or try to land one last hit on your.
Either way another hit or possibly two will finish them off. In the rare chance that they have managed to stun you/exhaust you/life steal you/jump out of a bush within close range to you, you have hopefully landed most of this burst and even if you die will be able to kill them back with your passive True Damage of 550.
Any enemy with less than 100 Armour and Magic Resist will surely die before than so feel free to go at squishier champs as long as there is no CC around.
As you can see through this builds very high AP and use of Sheen, Kog'Maw is able to be used as a highly damaging long rang harraser as well as a medium range burst killer.
Alternatives to build:
At the end of this build taking a second Archangels Staff rather than a Hextech Gunblade as your last item can be an option if you are finding enemies aren't rushing you worryingly and you are able to stay behind your team and poke effectively. The second Archangels will give you increased damage of 613 on your ultimate over 596 and also give 400 mana and 25 Mana/5. Which will allow you to fire off more Ults in succession especially if you have Blue buff, as it gives mana regen as a percent of total mana.
The arguments for Hextech Gunblade are:
The slow on it will allow you to run if necessary or to move to a safe distance to burst them down.
The stats on it will allow give you a lot more sustain, from your Artillery with 20% Spellvamp and from your auto-attacks and Lich-Bane lifesteal of 15%. There is also additional AD rather than AP which gives your normal Auto attack more damage however all your other damage will be slightly lower.
Another option for the Dual Archangels Staffs build is to at the end swap your boots in for a third archangels. This will give you another 234 AP at the expense of 78 move speed and 20 MPen. You could also swap Rylais for an Archangels
The other possibility is a trinity force for your boots, as it doesn't inhibit your speed as much and gives you a little more AP, AD, a slow and a few other defensive stats. Same again for swapping your Rylai's for this.
Of course the last 2 suggestions are only for very late game where you are already maxed and players builds become very polarised.
The last suggestion that I have to add to the build is to add a hexdrinker in early. This is a great counter to enemies with a lot of early AP harass and who come into AA range. Leblanc or Kassadin are prime examples of this. The fourth build is just for the items to display how this could be done.
Any other changes are really variating on the design and intent of the build, however if anyone has any suggestions on what might improve it then please do comment.