Passive - You Gain "fury" on autos and burrowed Q's which are consumed and replenish health while burrowed.

R - You can mark tagets by damageing them, while a enemy has a mark you can use the ability to quickly become untargetable and teleport to the marked champion. Dealing damage based on their missing health.best used for dives or if you need a minute of untargetability.

UnBurrowed Ablities

Q - An melee range auto emporment for 3 attacks that deal extra damage, best used in crowds for maximum effectiveness but isn't necissary.

W - Burrow allows you to enter the burrowed state, shortens you conventional vison range increases your MS and you cannot use basic attacks.Changes you to the burrowed moveset.

E - A single target bite that deals double and true damage when you have max fury.This is the basis and burst of rek'sai's damage.

Burroed Abilities

Q - A low damage high range and velocity projectile that reveals enemys on hit.Best used to be annoying for poke, and revealing people in bushes.


W - Unburrow can be cast without a target to knock up the nearest enemy, but is better used by auto attacking the target so you never miss.Also cahnges you to your unburrowed moveset.

E - Allows Rek'sai to create tunnels through or outside of terrain for movement which can be reused after a short cooldown and expire after a long time.They can also be destroyed if an enemy stands on them for long enough.You can deploy a max of 8 tunnels at a time, tunnels can be used to help traversing to lane,tunnels to mid, and usinng them to engage or escape.

Tank

Resolve

Aftershock - Allows you to gain some tankyness on your knock-up which is the central idea around your kit.

Font Of Life - Helps slightly heal frienlys when you hit your knock-up, Helpful in lane for your ADC

Slot 3 - This is more up to what you think you need against your matchup.I useally go with bone plating.

Unflinching -Due to Rek'sai's squishyness and weakness to CC I find its best to minimize its effectiveness even if only slightly, especially early game.

Precision

- this section is always up to prefrence but this is what I normally run

Triumph - Always take this, it helps solidify your escape after diving ability with R and helps when your in fights.

Legend:Tenacity - Same with unfliching i'll take this if I am facing a heavy CC support suchas Morg or Lux

Coup De Grace - Helps solidify your Kill pressure and Dive / Pick power.Normally I take this or last stand

Last Stand - helps kill opponents while your low, which you often are.

Boots

It's to to user discression but I prefer Plated Steelcaps and Merc treads

Tank

Turbo Chemtank - Due to Rek'sai's slow MS I find that I have trouble cathcing up to people to knock the up, so this helps compensate for your Move speed.

Sterak's Gage - Gives some much needed damage as well as some health to support Chem tanks passive.Sterak's passive also increses your ability to stay alive with its passive

Chempunk Chainsword - It seems taht every game there is some kind of Heavy Life steal or omnivanmp character so its just best to but this.(gives AD and health)

Everythig Else - Boots and items past this point are up to your match-ups and personal preferance, though I reconmend that you look for items with health gain or resistances after this point.
The items I build ae listed in the items section of the guide.

AD

Stride Breaker - Aides you in "stickyness" to your opponents to compensate for your MS to secure more damage and hopefully a kill

Sterak's Gage - Gives some much needed damage as well as some health to keep you alive.Sterak's passive also increses your ability to stay alive with its passive

Deaths Dance - This is your main source of resistance with its "Ignore pain" passive and 45 Armour while still providing some good AD.

Everythig Else - Boots and items past this point are up to your match-ups and personal preferance, though I reconmend that you look for items with health gain or resistances after this point.
The items I build ae listed in the items section of the guide.

I would Dedicate 3-4 Tunnels for getting to lane easier placing one on every back. Make sure that they aren't chained ontop of each other and have some space otherwise you wont travel consistantly between them.

If placed from alcove to the corner of the bush you can enter the tunnel from the Alcove bush and suprise enemy's attempting to destroy your tunnel.Works in the other bush as well with some accurate placement.

Just some tips

W knockup into Q autos until you have full fury for Q is a good standard Combo

If can always make sure to wait for full fury before you Q as this is the basis of your damage (Whats not to like about true damage?)

Don't all in if you can help it till 3 so you have a full damage combo and tunnels

Suprising people by tunneling from bushes or jsut the middle of lane is a good way of getting picks.

You can see your tunnel cooldown while in Unburrowed form if you look at the HUD Indicator

If you tunnel into a fight you need to be confident in your sucess becaseu you wont have much of an escape, that being said saving tunnel is a good escape meathod

Kinda like Alistar Flash Stun is always a opption you can even do this right out of a tunnel

You can still take burn damage and AOE effects like Morde passive while in R, so be wary fo this while your low on health

If you need a few seconds for your team to back you up your can R and hope help arrives or burrow after R and hope tunnel is up.

Tunnels will not allows travel what ever distance you want through terrain but to a legth limit so you wont be able to use long tunnels like you would Bard Portals