In this build i will tell you, how i play my Kennen and this works very well for me.
It may not work for everybody, but with enough skill and some time, you will be able to rock with this guide too.
There is one important rule for Kennen:
Use your Q-spell

Kennen is a 6300 IP hero and he is worth it. His autohits are ranged, that makes him a good harasser. The main attributes are:

- Ability Power: Every of his abilities scales with AP. This is the reason, it is the most important attribute in the game for Kennen. Especially in late game, you are one of them, who has to do the damage. To do this, you need a lot of AP, so get it.

- Magic Penetration: With Magic Penetration you do more damage against enemies with Magic Resist. This stat if in my opinion very needed in late game. When you are laning (doesn't matter if solo or duo lane), Magic Penetration isn't that important for me. But it will be, when your enemy gets some Magic Resist.

- Health: Kennen is generally not a tank, so he will be killed first. To avoid this problem you will need a lot of survivability. The only way to reach this, it to get some Health.

- Health/second: Not very important. You will just need it a little bit, while you are laning for not being forced to go back to your base.

The next thing about Kennen is: He is a ninja! Oh yeah ;)

First about, some things about runes:
There are more kinds of runes, one for every mastery-tree (offense, defense, utility)

Mark (red): Offense
Seal (yellow): Defense
Glyphe (blue): Utility
Quintessence: Everything

So every rune provides better attributes, if it is used for the tree it is made for. For some attributes, there are also two ways to get them: flat or per level.
With Kennen i take the flat runes. They provide a (flat) value, idepented from the champion's level. I prefer them, because they are better in early game and the harassment at the laning time is more important than a little bit more AP in late game.

So i decided to take the runes shown in the summary.

Why I choose the tank-tree ?
When you go utility, there are generally a lot of masteries, increasing your mana and mana-regeneration, but these are completely useless for Kennen, because he got energy. So you need to skill some masteries to get into the next tier and you lose some points for mana then. So it isn't that good.

As a caster,you generally just take the magic penetraion from the offense build. An then you go utility (with a mana-based caster). But for me, Kennen isn't as squishy, when he puts his points into the tank-tree and all the other trees are useless for him. So i go 9/21/0. An opportunity is to go 9/20/1 into Ghost. But I think, the reduced dmg-input is much better than the Ghost-mastery. So I decided to take Tenacity.

The items i go is just an advice and it will work very fine most time. This is a good build for Kennen:

Doran's Shield: Good for Early Game, because of the life regeneration
Boots: Running faster is very important and the increased magic penetration is also needed as a caster.
Scepter: Kennen hasn't got a slow, so he needs an item, which slows the enemies for him. So this item is also important for Kennen.
Hat: The Hat is one of the most important items for nearly every hero.
Warmog: I know, with this item you dont deal damage, but you need to survive a little bit in team fights, so i would buy this item in late game or you will die before you are able to use your ultimate.
Lich Bane: I just buy it for the passive and not for the attributs on it. With a lot of ability power, you will deal more damage with your auto-hits.

Like said, the Q-spell is extremely important for Kennen. It has got a little cooldown and just costs energy. This is the reason, you can spam it every time it is ready.

The Rush, i just take one time, because I only skill it for running faster and the higher ranks won't improve the running speed. So you just need it for adding a Mark of the Storm or running faster.

Electrical Surge is very useful for harassment, because every 5 attacks you will add a Mark of the Storm and then use this ability for doing some damage.

Kennen's ultimate is very nice. Skill it everytime you can and you can use it already on level 6 for ganking your laning enemie(s) by making damage with this ability, adding some Marks, using the Surge, throwing the Shuriken and get full energy again some seconds later. :P

I go for Ghost and Flash, because Kennen needs to be fast, especially in teamfights it is important for him to get with his ultimate to the enemies fast enought.
You can also take other spells, but Flash and Ghost are the best.

Pros:
+ hardcore harassment
+ nice last-hitting
+ no mana
+ good damage
+ not squishy (with this build)
+ able to stun
+ can take every lane

Cons:
- is often killed first
- can't jungle
- ultimate hits a random enemy (no focus)
- 6300 IP
- can't win the game alone

Jungling:

First at all: Kennen can't jungle!
So take a lane and dont try to jungle at all. In late game, you can kill the blue buff for cooldown-reduction and energy-regeneration, but let the mana-based champions take the buff, they need it much more.

Creeping:

Doesn't matter what lane you take and what enemies you got. I would always start with Doran's Shield because it helps you very much in early game. If you do it right, you will never need to go back, until the ganks start. So buy the Shield and wait for 1100 gold and buy the shoes then. For every lane, there is the same important rule: Use the Shuriken every time it is ready. Either for last hitting or for harrasing. You can also add your Rush and Surge very well to force your enemy porting back. Kennen has still no mana, so you can also use your Surge even if it doesn't do that much damage.
With your Rush you shoud also try to add a mark, but better dont waste it, because you will also need it to escape.

Kennen's ultimate is very awesome for teamfights, because it isn't a single target ability. But the problem with this ability is:
- When an enemy identifies, you used your ultimate, they will all focus you
- It deals damage to a random enemy, so you cant focus
To avoid this problems do following:
- Wait behind a wall, activate your ultimate and flash into the enemies, so they will recognise you too late
- Try not to hit all enemies. Try to only hit 3 enemies at the same time with your ultimate, so they suffer more damage from you and will be stunned. If you don't attack all of them, it is easier to focus the damage dealers.

I hope you will try this guide and like the way I play Kennen. If you like this guide, comment it pls. If you don't, comment it too please ;)
This is my first guide so i am not that experienced with writing guides.
Enjoy ;)
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06.04.2011: Publish