The way of the ninja is that of silence, stealth, getting in and out without dying, and face melting. This build is a test build I am using in LoL. Kennen has the abilities to truly turn any battle around just by showing up. And as quickly as he enters the fray, after faces are falling to the ground, he vanishes into the shadows from which he came. As I test this build out, i'll be adjusting accordingly, but this is the current build I use as I run through summoner's rift as the mini ninja.

Pros:
Very quick to get in and out of battle.
Easily lost in the confusion of team fights.
AoE Stun capabilities
Easily solos lanes due to range and fleet footedness
Master Farmer
Great Harasser
AP character not dependent on mana

Cons:
Squishy if caught (keyword if)
Best combo relies on a skill shot
Timing Timing Timing Timing Timing
Easily focused on if not hidden or located well
Cassiopeia.....

Ok, as I stated in my introduction, the following item build is what i'm CURRENTLY using in game. I'm testing them out and so far, this build does well for me. It is subject to change, and will change as I see it.

Doran's Shield You're probably wondering, "Doran's shield? Why not use something to boost your AP in lane like an Amplifying Tome or a Doran's Ring?" Early on, Kennen needs that extra toughness to keep him in lane. Even if you're able to keep your opponent at bay with your Thundering Shuriken, the extra health and armor makes a BIG difference in solo-laning adventures, as well as Gank scenarios. It'll keep you alive long enough to really start pumping in the AP.

Sheen After you get some Boots of speed, build Sheen as FAST as you possibly can. By the time you can afford Sheen, you should have Electrical Surge To level 2. We'll talk sequence later, but the sheer damage coming from Auto attack -> +50% magic damage -> Thundering Shuriken -> Sheen 100% base damage = Face Melting early game.


Sorcerer's Shoes Faster Movement speed, More Magic Penetration. Need I say More?

Malady The core of your shuriken tossing abilities. What Malady does is give you attack speed, which cuts procing Electrical Surge down a LOT. On top of that, your normal auto attacks NOW come packed with 20 magic damage, AND lowers the magic resist to your target by 6 for 8 seconds, which can be stacked 4 times ( - 24 magic resist ). It's gettin' melty up in here.

Lich Bane Now, with the magic penetration under your belt, time to unleash the Lich Bane. What that does is not only gives you a boost in Magic Resist, and a speed boost, you turn Sheen's 100% BASE damage into 100% AP damage. Add that to your Electrical Surge Proc, and it's really gonna start hurting.

Rabadon's Deathcap The 'creme de la creme' of AP. 140 initial AP with it + ALL ap by 30%? Yes, please, and thank you!

Void Staff I changed the positioning of Void staff for a few reasons. As awesome as the magic pen is, earlier in the game, it won't be THAT big of an issue. Later when builds start becoming finished and the team starts getting MR to start countering you, the void staff THEN becomes imperative. Not only does it give you a huge boost in AP, but it gives you +40% magic penetration.


Rylai's Crystal Scepter Time to bring in the big guns. This is the Frozen Mallet for AP players. Gives you a ton of health to keep you going, 80 ability power, and 35% movement speed decrease on your attacks. That's proced WITH spell damage, aka ANY OF YOUR ABILITES! Sadly, that will hit 35% with your Lightning Rush, due to your other spells being below 3 second cooldowns and hitting multi-targets, but hey, constantly spamming -15% speed on targets will keep them from getting away or too close.




Items for all ninja occasions:

The list above is amazing for one on one encounters. However, if you want more AoE and group damage, you can change out a few items to suit your face melting needs.

Malady -> Rod of Ages/ Moonflair Spellblade If nuking down a single target with Malady's attack speed/ap combo isn't your style, continue to raise your AP level with Rod of Ages. +20 AP and +180 health. On the other end, for just a pure boost in AP, go with Moonflair Spellblade. Gives you a +50 AP boost, and 35 tenacity can help any ninja escape with ease.

Lich Bane -> Morello's Evil Tome Lich Bane's job is to give you that added 100% AP blast from an auto-attack after an ability is used. Great for melting one champion. However, if you're wanting to go in and take on multiple opponents, you need less CD and more AP. Early game, Morello's Evil Tome is your best bet.

Mejai's Soulstealer If going one on one nuking isn't your thing, get a mejai's. The stacking of AP (max 160) will make you an Aoe nuking machine. Your opponents won't know what hit em when combined with Slicing Maelstrom, Lightning Rush, and Electrical Surge.

True Ninjas cannot allow themselves to get caught. Under ANY circumstance. To be caught is to forfeit one's life. These are the key Summoner's spells to helping you keep your Ninja head from being lopped off.

Ghost: The key to a good ninja is the ability to get in quick, do the damage, then get out before they realize who's melting their face clean off. Ghost is just that! Quick speed increase gets Kennen away from lumbering chasers like Sion or Olaf. Add that to the fact you can use Lightning Rush in sequence, or with it? Can't touch this.

Cleanse The OTHER necessary ability needed to escape. ESPECIALLY against teams with a LOT of CC. Stacked with Mercury Treads and CC is an after thought, not a threat.

Some ninja think differently than I do, so here's a couple of spells that you can opt in and out for the other two.

Flash The essence of "Ninja Vanish" in summoner skill form. You're probably wondering why I opted out of flash and chose Ghost instead. While Flash is a GREAT tactic and teleporting through walls will more often than not save you, more often than not, even flash, when used improperly, will not get you out of range fast enough. You can sacrifice Cleanse in attempt to being a 100% cocky ninja, able to run and flash away at ease. But in a CC led team, it's a fool's errand. Even taking Ghost out and relying solely on Cleanse and Lightning Rush is risky, but you ninja the way you wanna ninja.

Ignite A slightly reasonable summoner spell if you have lack of faith in your shuriken procs and skills. Only to be used for someone who builds Kennen more tanky. Ninja's need to be able to escape.

Heal Gaining back health is truly a skill that no one can ignore. Can help any Kennen in the most dire of times. Even without Cleanse or Ghost, it could give you just enough HP to survive long enough for Lightning Rush to come off CD. More for the gambling type of Ninja.

Exhaust For the truly aggressive ninja. One on one, keeping your prey from escaping can make or break your face melting. If you don't mind getting caught, or would rather slow your opponent down as you try to make your escape, Exhaust is not 100% unreliable.

The other spells are completely useless for Kennen, Save for 1

Teleport ONLY to be considered if you KNOW you are mid-laning. Getting back into the fight and defending your home turf is necessary by all means. The added bonus of showing up right when your team needs that last burst of AP to finish the opponents is a nice perk as well. If you MUST get it, trade it out with Cleanse. You still need to run if things get dicey.

For My Masteries, I do 21/9/0 for as much AP as I can squeeze out of it. The 9 into the defense tree help the little ninja survive longer (hopefully just long enough) to get the job done.

Offense Tree:

Summoner's Wrath 1/1: You'll be relying on you speed to get in and out quick. +35% to Ghost is a must

Mental Force 4/4: More Ap? Yes please!

Sorcery 4/4: Cooldown reduction makes for a shuriken happy Kennen

Alacrity 2/4: Attack speed to help quicken the pace to your Electrical Surge and Sheen / Lich Bane procs.

Arcane Knowledge 1/1: Magic Penetration to make your electric touch melt straight to the core of your enemies

Blast 4/4: MORE AP!? YES PLEASE!

Archmage 4/4: MOOOOOOAAAARRRR AAAAPPPPP!

Executioner 1/1: Make sure those hurting targets don't get away. FINISH HIM!

Defense Tree:

Hardiness 3/3: A less squishy Kennen makes for more face meltin'.

Resistance 3/3: Some say its futile. Going up against other AP opponents, it's necessary.

Vigor 2/3: Help keep your ninja in the fight with a little more HP regen.

Evasion 1/3: Spend that last point in evasion. Just might be the thing you need to win your AoE battle!

For my rune spec, I go strictly Magic Penetration with Greater Mark of Magic Penetration x 9, Greater Glyph of Magic Penetration x9, and Greater Quintessence of Magic Penetration x3. Pure and Straight penetration straight to your opponents core.

To help aid in the magic penetration, I also throw in Greater Seal of Ability Power x9, to give you a boost in AP. While most people like to add armor and health, I believe in melting their faces. In using this way of the ninja, you can't be killed by that which is dead (save for Karthus of course)

As Kennen, I prefer focusing on one enemy to make sure they die quickly and abruptly. After doing so, I speed out of there, normally leading the retaliating enemy reinforcements into my tank or ambush. Once that happens, I turn around, wash rinse repeat. I'll put my combo down starting from level 4 with Sheen.

I begin one of two ways: If i'm laning, I open use four auto attacks on minions. The instant I get to the fourth one, I wait until my target is in range. Then, I use Thundering Shuriken to begin the combo. This activates Sheen's 100% base damage attack on my next auto, which goes immediately after my Thundering Shuriken This also causes my Electrical Surge to proc, causing the NEXT Auto attack to hit with 50% additional AP damage. From here, if they are close, I hit them with a final Thundering Shuriken Stunning them, and finish them off with a final Sheen Proc.

Now, that seems like a lot to remember, and it kind of is. However, once you get used to it, it becomes second Nature.

Later on, once I get Lich Bane, I change things up a bit. At this point, i'm either aiming for turrents or i'm ganking. To gank, I make sure my Electrical Surge is Proc'd and ready to roll. I find my target and get in close with either Ghost, Lightning Rush, or patience. I open with a charged auto attack, with good initial damage, and a Mark of the Storm. I quickly follow up with a Thundering Shuriken, which is quickly followed by a Lich Bane Proc'd auto attack. At this point, they are set up for a stun from either my 'W' or 'E'. The stun lasts for 1 second, but that's more than enough time to finish them off with another Thundering Shuriken, or dash straight through them with a Lightning Rush to start the combo again.

As I stated, these tactics work wonders on solo opponents. Now let's talk about how to deal with a few opponents.

First off, unless the enemy is below half health, I don't recommend doing this alone. You may have the AP and speed to melt them down alone, but dying before you can get your finishing combo off will only make you look bad. Here's how you do it.

*note* always best to do this combo when your Ulti is up. If not, you'll end up only being able to stun up to two enemies if you are quick enough.

Before entering the fray, use auto-attack to where you next one will be proc'd with Electrical Surge. Stay hidden until you can dash in with Lightning Rush. Try to hit as many targets as possible. Immediately activate Electrical Surge to make sure all targets get nuked and get a second Mark of the Storm added to them.

At this point, there are two options: one WITH ulti and one WITHOUT

*With Ulti* Activate Slicing Maelstrom. All targets you hit initially will be stunned. At this point, aim for the lowest Hp target, or the biggest threat to hit them with your proc'd Electrical Surge for that finishing blow. Remember, while Maelstrom is up, you'll be hitting each of these targets 3 times. So by the time the third one is hit, anyone left standing is set up for a Thundering Shuriken to restun them or to finish them. By this time, Lightning Rush Should be off cool down. Either run away, or run through whomever you can reach or whomever is left to make sure everything dies.

*Without Ulti* This one takes a bit of timing and skill. After using Electrical Surge's active, find your biggest target and auto attack them. Having the passive proc from Electrical Surge will stun them. If that doesn't kill them, use Thundering Shuriken To finish them off. If it did kill them, Use your shuriken to stun your second opponent. If you have Lich Bane, That will proc and cause 100% AP damage on your next auto attack. By now, your third (if there is one) opponent will be on you. Ghost away slightly until Thundering Shuriken is up, and stun the final opponent. Your Lightning Rush Will be up, so you can either get out or keep at it.

If you have your ulti, you can easily handle the whole team. Without, typically 2-3 is your prime choice. Or do like me and just nuke one down, dash in toward the rest, ulti, wash rinse repeat. It's the best of two worlds!

Rather you want to take your opponents on one at a time and watch as they melt before you, or if you want to be in the middle of a giant melting symphony of lights, Kennen is a force to be reckoned with no matter how you play him. How will you choose?

NINJA VANISH! Kennen

Haven't updated...yet so doing so. Switching the sequence of items up slightly.