Hello Summoners, this is generally my first build even though ive played league for a while now. I wanted to do a kogmaw build, because you dont see too many good ap ones lately and i wanted to show the way i own with kog :P

When the prophet Malzahar was reborn in Icathia, he was led there by an ominous voice which thereafter anchored itself to his psyche. From within, this voice bestowed upon him terrible purpose, and though Malzahar was no longer tormented by its call, the voice did not cease its unrelenting summons. This baleful beacon's gentle flicker -- now fastened to Runeterra -- drew forth a putrid beast that ambled across a threshold it did not understand, widening a fissure between the spaces which were never meant to meet. There amongst the haunting ruins of Icathia, Kog'Maw manifested in Valoran with unsettling curiosity. The spark which led him to Runeterra teased him still, urging him gently towards Malzahar. It also encouraged him to familiarize himself with his new environment, to the stark horror of everything he encountered on his journey.

The enchanting colors and aromas of Runeterra intoxicated Kog'Maw, and he explored the fruits of the strange world the only way he knew how: by devouring them. At first he sampled only the wild flora and fauna he happened across. As he traversed the parched Tempest Flats, however, he came upon a tribe of nomads. Seemingly unhampered by conventional rules of physics, Kog'Maw consumed every nomad and any obstacles they put in his way, amounting to many times his own mass and volume. The most composed of his victims may have had time to wonder if this was due to the caustic enzymes which stung the ground as they dripped from his gaping mouth, although such musings were abruptly concluded. When his wake of catastrophe reached the Institute of War, an enthusiastic Malzahar greeted him with an enticing prospect: taste the best Runeterra could offer...on the Fields of Justice.

Skills

Caustic Spittle
- Passive: Increases Kog'Maw's attack speed. Active: Kog'Maw launches a corrosive projectile which deals magic damage and corrodes the target's armor for 4 seconds.
Passive: Increases Attack Speed by 10/15/20/25/30%.

Active: Kog'Maw launches a corrosive projectile which deals 60/110/160/210/260 (+0.7) magic damage and reduces the target's armor by 5/10/15/20/25.

Cost
60/60/60/60/60 Mana
Range
625

This is only going to be used when u engage into a fight as it reduces armour, but doesnt have much of a range and doesnt do very much damage.


Bio-Arcane Barrage
- Kog'Maw's attacks gain range and deal a percent of the target's maximum health as magic damage.
Kog'Maw's attacks gain 130/160/190/220/250 range and deal additional magic damage equal to 2/3/4/5/6% (+0.01)% of the target's maximum Health (Max: 100 Damage vs Monsters). Lasts 6 seconds.

Cost
50/50/50/50/50 Mana
Range
530

Going to be used in team and regular fights to last hit an enemy or target the tank, or someone with the health worth using this ability. This can be used for harrasment to hit the enemy enough untill they move in range of hitting you.


Void Ooze
- Kog'Maw launches a peculiar ooze which damages all enemies it passes through and leaves a trail which slows enemies who stand on it.
Kog'Maw launches ooze which deals 60/110/160/210/260 (+0.7) magic damage to enemies it passes through.

Additionally, it leaves a trail which slows enemies by 28/36/44/52/60% for 4 seconds.

Cost
80/90/100/110/120 Mana
Range
10000

This will be your main form of harrasment and farming at the beginning of the game as it can do massive damage and slow the target so u can combine it with bio arcane barrage for more damage.


Living Artillery
- Kog'Maw fires a living artillery shell at a great distance dealing damage and revealing targets. Additionally, multiple Living Artilleries in a short period of time cause them to cost additional mana.
Kog'Maw fires artillery from a great distance. After a short delay, the artillery falls dealing 80/120/160 (+0.3) magic damage and reveals targets for 4 seconds (deals 150% bonus damage to Champions).

Each subsequent Living Artillery in the next 6 seconds costs 40/40/40 additional mana (Max 200).

Cost
40/40/40 Mana
Range
1200

Form of harrasment, chasing, and last hitting/farming.

Icathian Surprise
- Upon dying, Kog'Maw starts a chain reaction in his body which causes him to move faster and detonate after 4 seconds; dealing 100 + (25 x lvl) true damage to surrounding enemies.

For Kogmaw, I put in Flat Ap Runes and magic penetration for major harrasing and killing early game.

I put in the basic 9/0/12 for magic pen early game and ability power over each level. The utility has mana regen and, cooldowns and buffs. Full buff duration to get the most out of your blue buff

I put in exhaust and ghost just for being able to chase and escape easily for a kill. Other useful spells can be teleport , ignite , clarity and heal . Clarity and teleport will probly be used more then ignite and heal for kog's mana issues when trying to harras as much as possible. And teleport for when u may be losing ur lane and need to get to it in a matter of time.

For items, i did flat ap and magic penetration for maximum damage. If anyone gets fed to the point of maxed out items ,start building full Archangel's staff and rabadons's deathcap ravadon's deathcap with sorcerors shoes.

Kog should always stay behind the rest of the team in a team fight. Kogmaw's abilities have massive range and no damage should be taken. First, Kog should throw in void ooze and caustic spittle, then back off a little to bioarcane the tank or someone building major health items. While throwing in his abilities, U need to spam ur ulti at the champs the entire time. This may seem a little bit of a mana problem , but i always try to get blue buff so u can stay in a fight as long as possible. For spells, try to exhaust the meelee/range dmge doing the massive dmge to ur team and only ghost when running from the enemy team or chasing one of the survivors.