My appearance may frighten you, but make no mistake—I am on your side, and we fight to the bitter end.

Claimed by Void Crest when she was only a child, Kai'Sa managed to survive through sheer tenacity and strength of will. Her experiences have made her a deadly hunter and, to some, the harbinger of a future they would rather not live to see. Having entered into an uneasy symbiosis with a living Void carapace, the time will soon come when she must decide whether to forgive those mortals who would call her a monster, and defeat the coming darkness together... or simply to forget, as the Void consumes the world that left her behind.

As an ADC the two most important things are to farm and not die... well thats all for this topic... :D. Just kidding.
Well i am not a pro, just started playing LoL for about 1 mounth, my normal main was MID (assassin) but a few days ago i started to find a liking in the champion named Kai'Sa, i found that she is similar to an assassin, HIT & RUN, and its very easy with her E and R skills.
In lane try to farm as much as you can because Kai'Sa is item dependent her evolves are awsome.
If the enemy tryes to poke you with theyr CC and fail go all in with your support, but be carefoul at the map so you always know where is the enemy jungle.
In team fight stay way back and wait for the right moment to strike, your R will help alot with that.
What can i say more... Kai'Sa is a fun hero (champion) to play so have fun and see ya in the rift. :)