Hey guys,
This is my guide about Tahm Kench.
I hope you like it.

Pros + Good late game + Much damage + Ult can teleport 2 champions

Cons - Mana hungry - He can get killed easily if he is out of mana - He is really slow

Mid/Jungle:

My red give me attack speed what i can use for my passive.
My quints,yellow.
My blue give me cooldown reduction what is good for my ult and w because they have a long cooldown.

9/21/0

I put 12 points in ferocity for damage and better jungle clear. I put 18 points in resolve for tank and so i can take less damage in jungle.

R>Q>W>E

First max your ULT for lower cd.
You want to max Q next because the slow increase will help you with ganking.
Max W third for the damage increase.
Max e last because the shield wouldn't change that much if you max it out.

Standard
You could replace flash with ghost but i dont recommend this

I start with Hunter's Talisman if i start on Red Side and with Hunter's Machete if i start on Blue Side.
After that i buy Stalker's blade so i can catch up people more easy and it is great for ganking.

I take Chinderhulk because i am a tank(you can take devourer to get 3 stacks on your passive quicker. I take Dead Man's Plate because it will give me much armor and health and it got a great passive. Spirit Visage is great against ap champions.
After this i will go Banshee's Veil, it got a great shield from his passive and it's good against ap champions too.

My boots depends on the enemies team. If they much champion with ap i take Mercury's Treads for magic resist and if they have much champions with ad i take Ninja Tabi for amor. You can choose Sorcerer's Shoes if you think you dont need magic resist/armor but more damage.

I finish my build with Randuin's Omen because the adc will deal much damage then.

Jungle Route:

Blue Side: First i kill Krugs. After that Razorbeaks and then Red Bramleback. You can take Scuttle crab after that for more gold.

Red Side: First i kill Gromp. After that i take Wolves and then Blue Sentinal. You can take Scuttle crab after that for more gold.

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Jungle Items:

Take Tracker's Knife if your team needs vision. Other take Stalker's Blade or Skirmisher's Sabre, Stalker's Blade for better ganks and Skirmischer's Sabre for more damage.

Passive:
An Acquired Taste
Tahm Kench's basic attacks and damaging abilities apply An Acquired Taste to enemy champions, stacking up to 3 times. Against enemies with three stacks, Tahm Kench's Tongue Lash.png Tongue Lash and Devour.png Devour gain additional effects.
After 7 seconds, An Acquired Taste stacks decay once every 0.5 seconds.

Q:
Tongue Lash RANGE: 800 COST: 50 MANA COOLDOWN: 6
ACTIVE: After a brief delay, Tahm Kench lashes his tongue in the target direction, dealing magic damage to the first enemy hit and slowing them for 2 seconds.
MAGIC DAMAGE: 80 / 125 / 170 / 215 / 260 (+ 70% AP)
SLOW: 30 / 40 / 50 / 60 / 70%
AN ACQUIRED TASTE: The target is also stunned for 1.5 seconds.
Tahm Kench can activate Devour during Tongue Lash to devour enemy minions or monsters from a distance.

W:

Devour RANGE: 250 COST: 90 MANA COOLDOWN: 14 / 13 / 12 / 11 / 10
ACTIVE: Tahm Kench swallows the target enemy minion, monster, or allied champion, making them untargetable and unable to take any actions for a short duration. Devour cannot be activated for 4 seconds after using Abyssal Voyage.
DURATION: 4 / 4.5 / 5 / 5.5 / 6
AN ACQUIRED TASTE: The target can be swallowed for half the duration, suppressing them, and applying Nearsight icon nearsight.
REDUCED DURATION: 2 / 2.25 / 2.5 / 2.75 / 3
While Tahm Kench has an ally in his belly, his ally becomes untargetable for the duration and he gains bonus movement speed towards enemy champions. Swallowing enemy champions Slows Tahm Kench by 95% and removes all An Acquired Taste stacks from them.
MOVEMENT SPEED: 15 / 17.5 / 20 / 22.5 / 25%
After a brief delay, Tahm Kench gains the ability to cast Regurgitate while his belly is full. Allied champions can exit at will.

E:
Regurgitate RANGE: 650
ACTIVE: Tahm Kench regurgitates the swallowed target. If they are an enemy, they are stunned for 0.25 seconds and take damage that is capped against monsters.
「 MAGIC DAMAGE: 20 / 23 / 26 / 29 / 32% (+ 2% per 100 AP) of target's maximum health 」
Minions and monsters are spat forth, stopping if they hit an enemy or terrain and dealing magic damage to all enemies around them and themselves before taking Regurgitate's damage.
PROJECTILE DAMAGE: 100 / 150 / 200 / 250 / 300 (+ 60% AP)
Allied champions are also spat out, stopping if they hit an enemy, while enemy champions are regurgitated at Tahm Kench's feet. Allied champions can also be spat out over small walls.

R:
Abyssal Voyage RANGE: 4000 / 5000 / 6000 COST: 100 MANA COOLDOWN: 120 / 110 / 100
PASSIVE: Tahm Kench's basic attacks and damaging abilities deal bonus magic damage.
BONUS MAGIC DAMAGE: 20 (+ 4 / 6 / 8% bonus health)
ACTIVE: Tahm Kench channels for up to 15 seconds, highlighting the path to his intended destination to allies while opening his maw to offer up to one allied champion the chance to come with him. Once an ally has climbed in or if Tahm Kench decides to go solo by Abyssal Voyage 2 reactivating Abyssal Voyage, he begins a 1-second channel which, upon completion, blinks him and his ally to the target location, arriving after a 0.5-second delay.
Taking damage interrupts Abyssal Voyage, putting it on a 10-second reduced cooldown. Abyssal Voyage cannot be activated while Devour his belly is full.
"Boy, the world's one river, and I'm its king. Ain't no place I ain't been; ain't no place I can't go again."
― Tahm Kench

Into a sunken town, the Handsome Gambler ran, for he owed gold and blood, and yet had none to spare. Desperate and forlorn, he was about to change his path and walk away, when he heard a song that called on him, to chance his luck again.

Now the singer was a creature, with the biggest mouth the Gambler had ever seen. "Excuse my song," the monstrous siren said. "The tune's purpose was your attention. For I knew you had troubles and I can offer absolutions."

"Can you carry me from this bind?" the youth asked.

"Boy, the world's one river, and I'm its king. Ain't no place I ain't been. Ain't no place I can't go again... And the price is a minuscule thing. See, I got hungers that ain't easily fed. But those finest tables? They ain't never got a seat for me. So I need men, like yourself, and let me in."

Now the Gambler's only hunger was dice and cards. So this bargain? It seemed too easy a price. "If you're offering a ticket," the youth finally said, "that's a deal I will take." And before another word was spoke, the monster snapped him up and fled.

To a faraway land the Gambler was conveyed. At a palace of chance, he was left.

Years passed. And love the Gambler found. His bride? a princess. And the wedding? None would miss.

Now when that hungry beast finally did arise: the family screamed and fought. And although the Gambler tried to cast him out... it ate the gifts, and house, and gold! For its hunger? Nothing satisfied.

"Please, not now, not this time!" the bride did cry.

The beast's response? To her it purred, "This hunger's a burden, but it's the last time, I swear. So please, forgive."

Now the creature's lies, so melodic and sincere, charmed that bride. And thus she failed to recognize when that demon's jaw unhinged. She screamed, just once. As I snapped her bones and crushed her limbs! Now that meal? It left me satisfied.

So cry if you want, boy, 'cause you had a chance to walk away. Instead you're the fool, the fool who let me in.

I think riot doens't understand he is a jungler and not a support.
He is a tank that deals much damage.
So my conclusion is that he is a really good jungler.

Updated pros and cons.
Tahm Kench top lane.
I will explain my runes and masteries better.
Video's.
Tips and Tricks.