Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
when needed sell Doran's Shield and Haunting Guise to make room for Void Staff and Rabadon's Deathcap
just go midlane, with you're offensive summonerskills you can get many kills in laning-phase, this is still before buying Mejai's Soulstealer, from the point you buyed Soulstealer you're probably in teamfight-phase.
try to gank in teamfight-phase to get stacks on you're Soulstealer, be selfish! just don't die when you've got 12-19 stacks, it would be so annoying to loose many stacks.
The huge amount of magicpenetration (40% Void Staff, 15%masteries) will ensure you that they'll need a LOT of magical resist before it makes any difference.
just play kennen a lot, mid- or side-lane, he's just awesome! xD
Thundering Shuriken - Kennen throws a fast moving shuriken towards a location, causing damage and adding a Mark of the Storm to any opponent that it hits.
Throws a shuriken that damages the first enemy it hits for 75/115/155/195/235 (+0.66) magic damage and adds a Mark of the Storm.
Cost 65/60/55/50/45 Energy
Electrical Surge - Kennen passively deals extra damage and adds a Mark of the Storm to his target every few attacks, and he can activate this ability to damage and add another Mark of the Storm to targets who are already marked.
Passive: Every 5 attacks, Kennen deals magic damage equal to 40/50/60/70/80% of his attack damage and adds a Mark of the Storm to his target.
Active: Surges electricity through all nearby targets afflicted by Mark of the Storm, dealing 65/95/125/155/185 (+0.55) magic damage and adding another mark.
Cost 45/45/45/45/45 Energy
Lightning Rush - Kennen morphs into a lightning form, enabling him to pass through units. Any enemy unit he runs through takes damage and gets a Mark of the Storm.
Kennen moves very fast and may pass through units, dealing 85/125/165/205/245 (+0.55) magic damage and adding a Mark of the Storm to any enemy he passes through. Additionally, Kennen will gain 10/20/30/40/50 armor and magic resistance for 4 seconds.
Kennen is refunded 40 energy if he passes through an enemy, but can only gain this effect once. Lightning Rush deals half damage to minions.
Cost 100/100/100/100/100 Energy
Slicing Maelstrom - Kennen summons a storm that strikes at random nearby enemy champions for magical damage.
Summons a magical storm that deals 80/145/210 (+0.4) magic damage and applies a Mark of the Storm to a random enemy champion near Kennen every 0.5/0.4/0.33 seconds. This storm attacks up to 6/10/15 times and cannot hit the same target more than 3 times.
Cost 40/40/40 Energy