Teemo, the swift scout

Lore:
Teemo is a legend among his yordle brothers and sisters in Bandle City. As far as yordles are concerned, there is something just slightly off about him. While Teemo enjoys the companionship of other yordles, he also insists on frequent solo missions in the ongoing defense of Bandle City. Despite his genuinely warm personality, something switches off inside Teemo's mind during combat so that the lives he must end while on patrol do not burden him. Even as a young recruit, the drill instructors and other trainees found it a little disconcerting that, while Teemo was normally charming and kind, he turned deadly serious and highly efficient the minute combat exercises began. Teemo's superiors quickly steered him toward the Scouts of the Mothership, which is one of Bandle City's most distinguished Special Forces unit alongside the Megling Commandos.

While most yordles do not handle solo scouting missions with a great deal of finesse, Teemo is remarkably efficient at them. His record of success in defending Bandle City from infiltrators easily makes him one of the most dangerous yordles alive, though you'd never know it by having a cup of honey mead with him at his favorite inn. Bandle City chose Teemo as their first champion for the League, and he has taken to it like a duck to water. His signature weapon - a blowgun - uses a rare ajunta poison he personally gathers from the jungles of ***ungu. To help cope with his lengthy periods of isolation, Teemo recently struck up a friendship with Tristana, a fellow League champion and fellow member of Bandle City's Special Forces. This connection is healthy for both yordles, though now Valoran's voracious media outlets circulate rumors that the friendship is turning into a romantic relationship. Regardless, Teemo is a crowd favorite in the League of Legends, and a pint-sized foe that many have come to fear.


"Teemo rides a thin line between chipper compatriot and unrepentant killer, but there's no one else I'd rather have as a friend." - Tristana


Basic information:
Champion cost: 1350 ip -- 585 rp
Roles: Assassin, Support, Disabler, Haste, Farmer, Ranged, Recommended, Scout

Pros:
Hellacious damage
One of the best farmers in the entire game (yes, I am looking at you mushrooms)
Nice early game, fantastic mid game, lethal (to the enemies) late game
Good pushing abilities
Tank destroyer
Can evolve into a fully capable ***asin late game
Can give map control to his team, which determines games
Mushrooms deal very good damage

Cons:
Quite squishy (though this build has been designed with his squishiness in mind, and attempts to counter it)
Mushrooms can be destroyed by anyone who has an oracle's elixir (in fact, in ranked/normal games every roamer will have an "eye" so a good team, with a good support who destroys your mushrooms will have you crippled as far as your team utility is concerned. Oh and btw even melee champs can clear your shrooms with an oracle's, as it doesn't need someone to come close for it to detonate, but to step on it.)
Has a tendency to be focused in team fights
Low health points
If your team has a lot of ap champs, and enemies build heavy magic resistance, you may begin to have some problems.

The reason I prefer to dive in to the defensive masteries is very simple: Teemo is neither a tank, nor a tanky dps. He is a dps (plain). That deals (heavy) damage. Enemies are aware of this fact. That's why it's nearly guaranteed that they will hunt you down in a team fight. Apart from that fact, early game you are squishy. A lot. And you need to cover the above points somehow. Plus I could not find anything better in the other trees. I mean, you can get the cd reduction and 15% magic penetration in offense, but save this there's nothing else to help you there. Arpen? Raw attack damage? But I deal magic damage. More crit damage? But I rarely (if ever) crit. Utility is even more meh. More experience would be good, but neither the extra gold nor the mana per 5 are worth the investment. And you will not need extra movement speed, as you already have more than 450 at level 18. Nothing more to say.

You need to max your Toxic Shot (E) but not asap. Take it easy. It synergises well with your on hit effects (actually that's why i build him on hit effects) but it doesn't count up if you do not have any on hit effects.
Your Blinding Dart (Q) is important but not for the damage. It's important because it helps you to counter hard attack damage carries and have some team utility apart from your mushrooms.
Your Move Quick (W) is not all that important, but it's passive is nice, and it's active even nicer. It has saved my butt countless times. The reason for that? The passive bonus is lost upon getting attacked by enemy champions or turrets. Whenever you activate the ability you get double the passive bonusses for 3 seconds and they can not be lost upon attacks from enemies. What does this mean? You can run away like a little girly while shouting "GTFO, GANKERS" xDDD
Your mushrooms Noxious Trap (R, Ultimate) are a whole chapter by themselves and will be covered

Hextech Gunblade:

Now, Hextech Gunblade is the #1 hybrid item in the game, but what can it do for Teemo you ask. Well, first of all, it gives your normal ad hit a pretty good boost of about 50 - 60 (depending on the enemies' armor). Apart from this, it will also give about 16 damage in overall to your Toxic Shot, about 60 damage to your Noxious Trap and another 60 to your Blinding Dart. Apart from these bonuses, it will also provide a boost to your survivability adding a 20% lifesteal and 25% spellvamp to your stats. All things considered a nice item on Teemo

What to replace: Wit's End
When to replace: When games take too long, and you happen to have some extra money to invest on it.

Void Staff:
What does a non on hit-effect, pure ap item has to do with as/on hit effects Teemo you may ask. Well this item only really shines if you happen to be part of a heavy magic damage team, or if the enemies build magic resistance to counter you. Stat wise it gives a +70 ap which adds to about 15 more damage in overall to your Toxic Shot and another 50 - 60 to your Noxious Trap and your Blinding Dart, and 40% magic penetration which is why you want this sweetness. It is only really useful, when enemies have way above 120 magic resistance.


What to replace: Malady
When to replace: When enemies have a lot of magic resistance.

Sorcerer Shoes:
You can get those case you want some magic penetration and your enemies do not have heavy crowd control spells and effects.

What to replace: Mercury's Treads
When to replace: When enemies have a lot of magic resistance.

Rylais Crystal´s Cepter:
A quite decent item on Teemo, actually empowers your Blinding Dart and your Noxious Trap by 65. But this is not the real reason you can use this item. The real reason is that it provides a decent, (even better than Frozen Mallet) slow. The only reason i choose Frozen Mallet in the main build, is that you can build it faster, and you also have a slow in your Phage while you build it. A decent item if you want the slow, and a little bit extra damage.

What to replace: Frozen Mallet
When to replace: When you feel like you want some extra damage in addition to the slow, and someone else can provide it while you still build it.