Aye, and welcome to my Kennen build. This build is based around Solo Top or Mid lane, and I wouldn't suggest it for a duo lane. It gives a mix of high damage and survivability. Please not that this is my first build, and I will try to update it, constructive criticism would be appreciated.

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I will add a banner, as soon as I can make/find one.

Pros

Great poke
Huge burst
Passive stun
AoE ult
Ninja

Cons

Squishy
Often focused

I always start of with Thundering Shuriken for the cheap poke, and the ability to check brushes easily with a well aimed shot. Try to poke your enemy out of the lane with it, if possible to deny him farm. Also useful if you didn't manage to last hit, and the minion is almost dead. I max this first.

At level 2 you should pick Electrical Surge, for initial poke caused by the passive. Every fifth auto attack you should aim at the enemy champion, for initial magic damage based on your attack damage. Combined with Lightning Rush it's extremely powerful for farming. Max this second.

I pick Lightning Rush at level 3, and let it there. The movement speed boost is nice, and it's great for farming. Also worth remembering is that it gives you extra Armor and Magic Resist, and it can potentially save you from Karthus's Requiem, or any other deadly spell in sight.

Kennen's Ultimate is godlike in teamfights, being able to stun an entire team at max rank. It can also save you in those times when you need your stun to get away, but you can't get three marks without it. Think of it like a mix between Fiddlesticks's Crowstorm and Amumu's Curse of the Sad Mummy, in that you both deal significant damage and apply crowd control effects to everyone around you.

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When a teamfight initiates, try to poke with Thundering Shuriken and Electrical Surge, saving Slicing Maelstrom until you know you're going to hit at least three enemy champions. Because of the high energy cost, I would suggest saving Lightning Rush in case you need to use your ult, or suddenly need to escape.

In lane try to harrass as much as possible with Thundering Shuriken and Electrical Surge, if you can harrass them out of the lane, denying them experience, that's good, but focus on last hitting, it will pay off late game.

For items, I start off with a Doran's Shield, and try to stay in lane until I can afford a Needlessly Large Rod. After that, I try to rush Mercury Threads before completely finishing my Rabbadon's Deathcap. After that, I go for a Rylai's Crystal Scepter for the survivability, and the passive slow. Then I go for a Guardian Angel, an extra life every five minutes, is not bad, plus it gives you lot of defense. If the game is not yet finished, I build Zhonya's Hourglass, use it with your ult on, stunning everyone in reach while not taking damage.

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The Core

These are the items I always build, the rest is situational, depending on the enemy team, and how well you're doing.

Rabbadon's Deathcap For the high amount of Ability Power plus the passive.

Rylai's Crystal Scepter The main item of this build, high survivability, decent amount of AP and a passive slow.

Other than that, the most is situational. If the enemy team has no crowd control, you won't need Mercury's Threads and Sorcerer's Shoes would be a btter choiche. Same goes for the rest of the items, however I would focus on pure AP, not so much on cooldown reduction, and obviously not, mana.

Luxury Items

This are items you can buy if the game lasts for longer than usual, and you got lots of gold. I would suggest a Will of the Ancients, or if you got enough gold, a Lichbane. If you know the game is going to last even longer, you could get a Rod of Ages. If you for example, got Sorcerer's Shoes instead of Mercury Threads, you could get a Moonflair Spellblade.

I take pretty standard AP Caster runes, focusing on a mix between survivability and damage, at all stages of the game.

Greater Mark of Magic Penetration for the extra damage it gives you late game.

Greater Seal of Armor for survivability.

Greater Glyph of Magic Resist also for survivability.

Greater Quintessence of Ability Power for the extra damage troughtout the whole game.

For Solo Top I take 1-21-8 Masteries, for the improved Ignite on Offense, the extra survivability and movement speed in Defense, and even more movement speed in Utility. If you're heading Mid, I would suggest 21-1-8 Masteries instead, focusing more on damage.

For Summoner Spells, I like to take Flash Ignite, both Solo Top and Mid. If you know you're going to have a 1v2 lane top, I would suggest either Flash Cleanse or Flash Teleport. If they got much CC, I would go for Cleanse, but if they have a lot of pushing power, but lack CC, go for Teleport.

Recommended Summoners Spells

Great for escaping, still post nerf.

Can't say no to extra damage!

Yet another great escape spell.

Get back to your lane in no time!

Chase or Escape.

78 more Ability Power at level 18? Yes please!

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Not Recommended At All Summoner Spells

May I remind you that Kennen uses Energy?

If you feel you need this, you're doing something wrong!

This got nerfed too bad, and to top it off, you're not even a support champion!

Kennen

is a strong AP Caster, which huge burst, and great poke, with longa range, low cost, and low cooldown. He's got a great AoE Ult, and can be a monster both in lane and in teamfights. He has a passive stun, and has the potential of stunning entire teams, if positioned correctly. Kennen can take any lane, both solo top and mid, and babysit bot.

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