Hello my name is Rep Sup For KS and I am Support / Mid Main, but i play many other champs too! I have been playing League of Legends for now about 3 years now. I hope this guide will help you! If you have something to ask, just tell me!
I will be adding THREATs when I play against them!

I will update this Guide when i have time

I sometimes forget Mobafire, so my guides can sometimes be inaccurate...

Tahm Kench is currently super strong, because THIS build!. I recommend building first Riftmaker, because it gives you Omni Vamp 8% and it deals much Ability power +80AP!

Hail of the Blade

Hail of the Blade is OP on Tahm Kench because it will make your attack speed so fast and you can use your Devour almost INSTANTLY!
I recommend using Cheap Shot or Taste of Blood, you need more Lifesteal.

Resolve

On second runes, I recommend Resolve, because it will make you more tanky. Bone Plating will give some shield when attacked and Shield Bash will give you Armor and Magic Resistance when shielded! Shield Bash is very important rune for Tahm Kench because you have ability to give yourself Shield!

Devour:

You can use your Devour to get behind your enemy.
Also you can take your teammate with you, so it will be easy kill!

You can use Devour for escaping enemies and you can take your teammate with you!

An Acquired Taste:

You can stun enemies with your Tongue Lash when enemy has red fish on him.
Also you can use Devour on enemy when An Acquired Taste is ready.

Devour:

You can save you teammates with Devour. Devour is very good if you're playing support, but can be used to save your teammates without being support.
You can also use Devour on enemy when you have AA him several times to obtain An Acquired Taste. You can see red fish on enemy when An Acquired Taste is ready.

Thick Skin:

When you have Shield Bash, Thick Skin will give you some extra Armor and Magic Resistance!
Thick Skin will help you survive 1v1's and any fights, so its very important to use in right time or you will die.

Pros:
You will deal much damage.
You can roam with your Devour.
Very easy to play!
Rarely banned!

Cons:
You might useless in late game.
You have to know how to use your Devour