I need help. I want to learn 3 champs

To learn how to play riven. Just watch box box on twitch. Hes prob the best riven player in the world other than faker.

I can help you with Kha'Zix. High Burst Damage Assassin Ability Resets when target is killed.

With that being said, when it comes to team fights, it's your job to come from out of the fog of war and completely blow up your target. Kha'Zix is a very mechanic based champ, so your positioning with engages, and team fights is crucial. Always target squishy champs. Always target ADC Mid champs. Avoid heavy engage with strong CC compositions. Being the first one to engage against that type of composition will get you killed. Use your ult to pick off individual targets. By individual I mean separated from the group. Your passive allows for you to do more damage.

I hope this helps

Solomid.net lolking.net

Both places have guides.

Nightblue3 for the Kha'zix and Rek'Sai....look him up on youtube, he has guides out there that shows you how he plays those champs, what he builds etc.

people write the guides... people who have the a lot of experience with the champ take the time to write out everything they've learned, break it down into categories, illustrate ideas with pictures and videos...

Just check out a guide bro, no one's going to put that much effort into a forum post :p