My Personal Guide to Kennen the Heart of the Tempest.

Head over to Kennen!
Pros:

Excellent Mid/Solo Top Champion.
High Damage output.
Underestimated.
No MP issues.
(Best Dance :D)

Cons:

Squishy
Hard CC = Dead

My Rune Setup isnt that common but it fits my personal style.
Greater Mark of Magic Penetration
Greater Seal of Vitality
Greater Glyph of Magic Penetration
Greater Quintessence of Magic Penetration

19 MPen allows you to almost deal true damage with your skills @ Lvl 1, and ongoing my build Focus on beeing able to do as much damage as possible due Magic Penetration.

My Masteries (9/21/0):
9 Points in offensive for MPen/CDR/AP
21 Points in defense for Ar/Mr/Dodge/HP/AP%

You need the defense to compensate your low range skills.
I do not recommend to go 21/0/9 or 9/0/21!

For Items i recommend to start with: Boots and 3x Health Potion.
It allows you to stay long enough on the lane to farm aswell as dealing with the enemy champion. You also might want to start with Amplifying Tome and 1x Health Potion (do this if you know you will dominate your lane).

First Trip back you should have enough money to buy:
Needlessly Large Rod
2-3 Sight Ward (or Vision Ward)
(If possible due early Ganks/First Blood: Sorcerer's Shoes)

Keep on farming and ganking till you have enough money for:
Rabadon's Deathcap
Sorcerer's Shoes

At this point you should be around Lvl 11 with 39 Magic Penetration (+15% due Masteries) and around 200 Ability Power, now you should be able to deal (almost) true damage to the most enemy champions.

The Enemy's will now be forced to buy Magic Resist Items (if they dont want to die), to counter this you will focus on: Void Staff, this items allows you to continue deal a huge anmount of damage.
They might be will focus you due teamfights, for that you need to buy the Zhonya's Hourglass it allows you to deal full damage with your ultimate aswell as beeing untouchable for 2s, its a great item to counter any focus on you.

Note: Most of the games might be ending up after you bought Zhonya's Hourglass, if not keep on building the following item's:
Abyssal Mask a great item to increase your damage aswell as increasing your Magic Resist and decreasing the Magic Resist of enemy champions which will increase your damage further more.
Rylai's Crystal Scepter Huge HP/AP Ratio, and it adds a slow on your skills, which is awesome for chasing down a single enemy champion.

Items which may be good if facing huge anmount of CC on the enemy team:
Quicksilver Sash awesome against any type of CC
Banshee's Veil good against cc, also gives HP, but i dont like the face that we paying for MP on this item.

Its your choice, i prefer Quicksilver Sash.

Good Summoner Spells:
Flash or Ghost
Ignite or Cleanse

Most of the times i use Flash and Ignite.
You can use Flash to:
Escape ganks.
Place yourself better for Thundering Shuriken .(do this only if you want to secure a kill)

Ignite for:
More damage aswell as countering Dr. Mundo Warwick Irelia Fiddlesticks Vladimir.

Cleanse to:
Counter hard cc

At Level 2 you can start stunning your oppenent:
Save your free Mark of the Storm from: Electrical Surge, start with Thundering Shuriken if its hits follow up with Electrical Surge + the free Mark of Thunder from Auto Attack, keep doing damage until he use his Flash if he comes back ask for a gank and tell your team that he hasnt Flash ready.

At Level 3 you can start zone him, wait until he wants to Last Hit a creep, run into with Lightning Rush, follow up with Electrical Surge and try to land your Thundering Shuriken, if you not land it, keep Auto Attack creeps for your free Mark of the Storm from Electrical Surge.

At Level 6 you can easily kill the enemy champion on your lane, start with Lightning Rush follow up with Slicing Maelstrom to finish the stun Electrical Surge, now use Thundering Shuriken he still should gain Mark of the Storm from your Slicing Maelstrom, dont forget to keep hitting him with Auto Attack to gain the free Mark of the Storm from Electrical Surge

Note: If he use Flash to escape you can use Flash to get to him again, but make sure your out of tower range!

Farming with Kennen is somewhat importend. Due the low cooldown of Thundering Shuriken you can use it to farm aswell as punish the enemy champion.

Malzahar - Hard to lane against, his DoT is annoying, if you have trouble ask for a gank or buy Spellvamp Items like Will of the Ancients! You might also want to buy a Negatron Cloak to not get one comboed at Level 6!

Annie - Somewhat easy, just take care of her stun, do not overextend while she has 4 loads! Buy a Negatron Cloak earlier as you want to, to not get killed by her tibbers burst!

Swain - Against Swain you need movement, if you get caught in his snare, your almost dead, at Level 6 you need to ignite to secure a kill/gank! Buy the normal item route!

Anivia - She is pretty neat, hard to gank, concentrate on dodging her stun, and keep on farming, never underestimate Anivia, she has such a high burst!

Katarina - Easy to dominate her, punish her Shunpo with a Lightning Rush, try to deny exp/gold, but take care when she hits Level 6, her Death Lotus does good damage even without strong items.

Kennen has a huge impact on teamfights, he is able to stun/disable the entire enemy team.
But never initiate with Kennen you will be dead within 1s, always wait for your team to initiate.
If the enemy team initiate, stay back to not be focused, its also wise to stay behind a wall you can Flash over. they maybe dont expect you, Flash over and Lightning Rush through them, turn on Slicing Maelstrom if they focus you never forget to use Zhonya's Hourglass now watch 2s how your team is able to kill the entire enemy team :)

Kennen is in my eye's the strongest AP Champion, he's able to turn a whole teamfight around!

Never underestimate the Heart of the Tempest.

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