1t:
Don't take Flash with this build it will kill you. You only need Ghost and Cleanse. No other spells will realy work with this build.

2nd:
After requested here I created this tiny guide.
Its tiny cause i dont want to reval my complete playstyle. You must "master" this build by yourself i just giving little hints to do so.

3rd:
My english is bad + i got dyslexia. So if you want you can search for errors and post them in the comments. I will fix it then.


This Kog Maw build need alot Manaregeneration! Any abillity power is good but not needed till mid or late game. The ability to spam your Living Artillery rly fast will compensate the lack of the missing ability power.

Like mention above:
You have to Pick
Cleanse
and
Ghost

You can test the other spells but it didn't worked for me.
If you want you can take Teleport instead of Ghost. With teleport you can support your team in the early game alot better.

Never take Ignite or Flash!
The range of Ignite is too short. If an enemy is coming that close to you and if you are in the need of this extra damage its already too late anyway.
Flash can maybe save your butt for few seconds but then they will get you because you are a slow little pig.
Additionally you will be far away from any team fights anyway. So you don't need to flash out of enemies! You will stay in bushes or behind thick walls and give your team artillery support.
If an enemy get you there you should be able to cleanse his disables and kill him while you try to escape from his attack range.

In the most emergency cases you will find yourself running for you life to reach the next tower to beat the enemies up while they try to push it or you will chase enemies down that are far away from you. But normally you will just stand somewhere in the desert and press Living Artillery and sometimes Void Ooze. So how could be Flash and Ignite be of any use for you?!

This is the most important part.
As you may see above you have to sell some items in the late game.
You will switch your Eleisa's Miracle for the 2nd Archangel's Staff or Void Staff
You will switch your Chalice of Harmony for the 3rd Archangel's Staff or Void Staff

If you want you can switch your Sorcerer's Shoes for a 2nd Lich Bane. I dont recommend this cause your movement speed will be around 375.


If you are selling you Chalice of Harmony you will lose the ability to shoot for as long as you want with your Living Artillery even when you have the blue buff. You have to keep that in mind! But your mana should last for maybe 10-20 rapid fired shells

You will take the Mid Lane. Your most important skill is the Living Artillery. you will do alot bad stuff with it. It can be used in many ways, i will just reval this: Just spam it! After 3 or 4 games your enemies will fear the "Wuuuarrggg Wuuuarrggg Wuuuarrggg Wuuuarrggg Wuuuarrggg" sound of your Living Artillery rapidfire and you will love it.

Ban Shaco and Nocturne. Those guys will be a really pain in YOUR ***.
If those guys get in melee range to attack you while you don't get any help, your escape chance are below 20%. I recommend a "Stand and fight" tactic in those situations, your chance to beat them up is 30/70 and with a Lich Bane it will be around 80/20.

If the enemy banned Rammus and Amumu already you can ban Soraka. She can heal with one ulti nearly all damage you have done before and she is even without her ulti a really good counter against your Living Artillery. But the best way to deal with her is to find someone in your team that will pick soraka for your team before the enemy can pick her.
Other enemy supporters like Sona, Karma and Janna are no problem.

If you want you can ban Akali, Kassadin and Talon but those guys are alot easier to handle for you and they dont will be any real threaths for you in most cases.

Don't ban Vayne, Annie, Xerath, Ashe, Ahri, Fizz. Your E and/or R skill is a perfect counter to keep distants to them and kill them with ease. Xerath is just a alot worser version of you, he cant stand a chance against you after the late "early game"


Early Game:
Use your Void Ooze to harras a little bit the enemy. Allways stay out of his attack range. if he try to get closer use your Void Ooze to slow him and run away from him. if he is defenless while he is on your ooze attack him with autoattacks and Caustic Spittle.
Concentrate on farming not killing the enemy mid player. After reaching lvl 6 and getting the Chalice of Harmony you can farm a whole creep wave with a smart use of your Living Artillery and Void Ooze.
Remeber stay defensive dont cross the the middle of your lane if possible.

Late early Game:
You will dominate the enemy mid player by now. kill him if possible, in most cases you dont have to cross the middle of your lane doing so.
Stay defensive

Mid game:
Try to reach lvl 16 as fast as possible and then get the blue buff then. If you manage this you have for a short time a giant advantage. Most of the enemies will lose 20-50% of their hp when you hit them with your Living Artillery. And now you can spam it till the blue buff last. Use it to win the game or push as much towers as possible!

Late game:
Get the Blue buff push mid with your team


Teamfights:
Stay out of enemy range and spam Living Artillery
If you really want to help your team as much as possible shoot a Void Ooze through the enemy team and do as much aoe damage as possible with your Living Artillery.
if someone comes to close try to nuke him, if Void Ooze is on cd melt him with Bio-Arcane Barrage and Caustic Spittle.
If enemy tank is trying to initiate give him the proof that this was the worst decision he could made:
1st Void Ooze, 2nd Caustic Spittle, 3rd Bio-Arcane Barrage and finally some Living Artillery.
This will kill him or cost at least 50% of his hp.

Avoid teamfights far away from the lanes:
Team fights around the red buff and blue one are your absolute weak spots! You are an artillery that needs a clear sight on the enemies and you don't wanted to be ambushed from the flanks.
Always try to bind the enemy team on the lane. if they are at the lane and pushing your tower or guarding their tower you have a big advantage. Its like hunting sitting ducks!


Teammates:
Perfect teammates are all guys with stuns, snares, slows and aoe disables and if possible some extra hp.
For example
Cho'Gath, Amumu, Leona, Gangplank, Sona, Alistar, Galio, Nunu & Willump, Jarvan IV, Nasus, Maokai and Irelia.

You gain more and more advantage as more static a teamfight is and as longer it last!

Thats it! With this knowledge you should be able to test it and after 10 games you should know all cons and pros of this build.