Rek'Sai is a really powerful counter jungle and can control the map really hard.
First of all is really important to use W in almost every case to control enemies position.
You can risk yourself in counter jungle with Q and E.
I always keep my E for escape instead if there is an easy kill or I want to get an adventure haha.

For runes I take %AS because I start in krugs and smite them.
I take ad runes too like normal's ad's junglers and armor.
I have a 5%cdr and it's really useful to spam q!
If your team helps you there it would be easier for you to clear the jungle.
Try to do the jungle as faster as you can, unless you can do an easy gank!

Try to use your passive as much as you can, but firts try to deal the real dmg from E with all your fury and see when you can stun monster again with your W.
When you can stun them again try to dig and run away a little from the monster to heal yourself receiving the less dmg you can. Then use Q and W again to stun them!
Here is the route I always do:
After you clear the jungle for first time maybe is too risky to gank, but if you see a really pushed line or and easy kill go with your W and E and stun him! It's better to recall with a kill/assist :)

You can't reach your target? Try to smite it! or use E and then flash and W!

Hope u like it!

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