Kennen questions

IMO the only thing he is useful for mid/late game is his ult. A good ult will carry a teamfight.

+Ult+

That's all you need to know

Kennen is an energy type champion. Energy differs from mana in that it regenerates quicker, but you don't have as much of it, so you don't really have the capacity to burst a champion down. This means you can stay in lane longer and deal more damage over time, but you don't have lots of short term damage potential. Kennen differs from other energy type champions due to the fact he is mostly ability power and the fact he is ranged. He relies a great deal on combos for damage thanks to his passive. Utilizing this combo has risks: his only escape also applies stacks of his passive, and is the most efficient way to initiate. This leads to difficult choices when planning to either attack or flee.

He's sort of a high team fight potential lane mage.

He is just a really funny champ with burst and and an amazing teamfight but only if you know how to find good ults. I would definitely suggest him if your good at making split second decesion making.