Hello readers, this is my first guide on mobafire and I'm pretty happy about this.
This guide is not going to be a fancy guide like all the other ones on mobafire, but just a quick one to explain how to play Rengar (kinda) and how to build him during the game.

Rengar is a high mobility assassin with a low CD ultimate which gives you a very nice stealth and stacks of your unique resource: Ferocity.
Instead of having mana or rage or energy, Rengar builds up Ferocity which is built up by using your spells up to a maximum of 5 stacks, when you reach max stacks your abilities will gain additional effects.
I guess that's all for the basics of Rengar

Pros
Very mobile
Very fun to play
He can one the carries
Stealth
Low CD ulti
and a lot more

Cons
You might need some time to master him properly
He can be shut down with some champions
Oracle's a *****

This is going to be a quick Matchup section of the guide.
There are some champions which you will hate to play against such as
Renekton and his ugly lizard face
Riven and her ******* giant sword
Jax and his dodge
Malphite because his ****'s rock hard
Pantheon and his block
Lee Sin and his blindfold

These are my everydays runesIf you are facing an AP opponent just switch your armor runes with MR, Attack Damage is a must though.

For masteries I really like and play very well with these:

Now to my favourite part of the guide: the itemization.
As we already said, Rengar is a high mobility assassin and he can be built in different ways.
At the top of the guide you can obviously see which items I pick and now I'll explain why I pick them.
I guess there's no need to explain the Cloth Armor and pots so I'll just skip to the Doran's.
Doran's Blade are a great item due to the health and early damage they give you, you can dominate the enemy and snowball the lane after a single kill.
Bonetooth should be built right after the Doran's so you can stack it on the early game, the best buff it offers you is the armor pen with 3 stacks.
Black Cleaver is one of my all time favourite items and I buy a complete one whenever I can as a first item because it procs with your Q and your high attack speed (provided by your Q).
BotRK is a very good item for you since you will be jumping on people's head and carve a souvenir out of them, it also gives a nice dueling potential.
Last Whisper provides an unbelieavable amount of Armor Pen and I simply love it.
The last item is most likely Hydra or GA but I like the YOLO mode on Rengar and Hydra gives you damage, life steal, health regen and AoE damage.
Do not forget the boots though! I usually buy Mobility unless they have a lot of CC.

The difference between a Rengar and a good Rengar is the triple Q.
As we already said when Rengar gets 5 Ferocity stacks his abilities gains additional effects and Q's damage gets increased.
You may not be aware that you can actually do it three times instead of just two.
To do so you need at least three stacks, activate your ulti, wait for five stacks, activate your q, wait for two stacks again and spam every single spell until you are fully stacked again.
And that's GG, you just killed the enemy carry.
http://www.youtube.com/watch?v=d5aNn6_Jybs
Just in case you didn't understand it, watch this video.

As we said many times, Rengar is a great assassin but what can he do in teamfights?
It's simple, he kills the carries with the Triple Q and he runs away with their heads.
Rengar is especially good in split pushing due to Q's damage, and the key to win in Solo Q is the split push, most teams won't be coordinated enough to stop you and if they try to kill you, just pop R and run away. But do it with style.

The hunt is on is a special quest between Kha'Zix and Rengar, when they are both 16 and Rengar has either free space in the inventory or the Bonetooth the first one to kill the other will complete the quest.
Kha'Zix will gain every single upgrade on his abilities and Rengar will get a fully stacked Bonetooth and he can't lost stacks on death, but most important, he gets Kha'Zix's head.

I guess this is all for my first and most likely last guide on Mobafire, so thanks for reading and have a good game in the Summoner's Rift.
P.S.
Do not forget to carve their heads.