Hello everybody,

this is my own personal version of a Mecha'Thun Warlock. It is based on the mechanical old god as a primary win condition, using both Genn Greymane and Reno Jackson to ensure victory.

Isn't an Even Reno Mecha'Thun needlessly complicate?

No, it isn't. Every part of this deck makes sense. The first thing that makes sense is Mecha'Thun: this deck has been created to have a deck that has Mecha'Thun as his first and most reliable win condition, a real combo warlock, instead of a Control Warlock with Mecha'Thun put inside as a bonus. And remember: people will see Genn in the first turn, so they'll think you are a netdecked even warlock. Then, they'll see either Reno or Kazakus, or other strange card usually not played that much: they'll think you are an original reno deck. People always think with popular decks in mind, they won't realize you are a Mecha'Thun until it will be too late.

Wouldn't it be better to play Voidlord, Mal'ganis, the Death Knight, other powerfull odd card, Ben Brode, a blue eyes white dragon?

Maybe yes. But it wouldn't be a real combo mecha'thun deck if you win with things that aren't your combo. This is a combo deck and not a control deck. I don't care about win rate, I care about the fact that you can play mecha'thunlock as a pure combo deck if you want to.
However, the voidlord can make mecha'thun miss, while in this deck the combo never misses. The Death Knight will take over your main draw engine, that is your first win condition.

How does it works?

It's easy. You use the (1) mana hero power to draw all your deck, playing your minion to get some tempo; when the combo is ready and the last card has been drawn, you have won.
You must play Emperor Thaurissan when you have in your hand both Mecha'Thun and Bloodbloom. Then, when the deck ended, you play (9) Mecha'thun, (1) Bloodbloom, and Cataclysm. The deck is built so the state of your board never makes you miss the combo.

Why Even?

Genn assure us the most resources possibles. All the combo is even, as Reno and Kazakus. (1) mana hero power is fast and cost the least tempo ever. So it is a very good draw engine.

Why Reno?

Because Genn cost you much health to draw cards, you need some serious healing. Reno is perfect, as for the nature of Mecha'Thun, you'll draw all your deck eventually, and this mitigate the highlander restriction. And Kazakus potion is really strong, expecially versus Big Priest.
And don't remember that in some match-up Zephrys the Great can be a secondary win condition.

The parts of this deck:

• The combo: Mecha'thun, BloodBloom, Cataclysm, Emperor Thaurissan. You need all 4 to win in a single turn. Pay attenction that a Dirty Rat on Thaurissan doesn't make it over, as you can still win in two turns, playing Mecha'thun first and then Cataclysm.
• The draw: you have some card draw because you want to end that deck fast, really fast. You need to be faster then other combo deck, faster then control deck trying to kill you. So the hero power alone isn't enough. Then, most card draw have a body, and every damage a minion takes instead of your face is a step nearer your win. People trade too much because they think you are an even warlock, so you should take advantage of this while drawing and moving forward your goal.
• The heal: this is a deck that lives on the edge. You need more healing then Reno alone. And as for the draw minions, healing minions have a body your opponent will trade.
• The control: you play some aoe like defile or Twisting Nether, some damage like spellstone. You should use this to control the board while drawing. This will make you last until the end of your deck.

How to play this deck: against aggro

Against aggro your main win condition is Reno Jackson. You will draw fast, so you will draw him in time, hopefully. The draw minions will help you trading, while defile, hellfire and Kazakus' 5 mana potion will make opponent stay under control. You have a good healing, so you'll make them deplete their resources, without needing to play your combo. Zephrys the Great can be used as a board clear or for survival tools.

Against control

You there should draw as many card as possible, using your hero power optimally every turn. The sooner you end your deck the sooner you win, after all. While you are drawing, you should play minions and spell to try to make everything go round. Card like Reno, Kazakus' ten mana potion, Twisting Nether, syphon soul, will help you against everything your opponent will play. Your goal here is survive. Just survive.
Pay attention to Zephrys the Great in some longer match-up, expecially against warlock, because there are some game that can be closed with the help of a "perfect" card. In other case, he can be a second Twisting Nether, that is often more then enough to reach your Mecha'Thun win condition.

Against midrange

There, you are slower, so you should capitalize your draw power. This works like the control match-up, as you will need to play your combo to win. Except in some cases. But as you play a very low count of big minions (a Giant and Genn aren't nearly enough), you will steal some victory but your main win condition is still the combo. That's why we like this deck after all.

Against combo

Draw, draw, and draw again. You can be faster then them. As they won't try to kill you without their combo (because they won't realize in time you are a Mecha'thun warlock and not a even or reno warlock), you should draw everytime you can. End the deck before they get their win condition = you win.
Said that, this deck play dirty rat + syphon sould or blastcrystal potion to use for steal some win.

Against Big Priest

The match-up is hard as we can't play any tech card against big priest, except Kazakus' potion and gnomeferatu. May the force be with you.

Final consideration

This is a smoke deck, a deck that mimic another archetype to make the opponent confused. Depending on their ability, they won't understand what you are playing at all until the end. You are an even deck, after all, they see it since the very beginning; so they'll keep some card for the unavoidable Giants you will never drop. After you have played Reno or Kazakus, they'll keep that hex for the Rin that you will never use to win. Even after you play Thaurissan they won't be sure about your true nature. This is the real power of this deck.
Ok, maybe it won't work against Disguised Toast. But how many of you are in US high legend, anyway? :P

PS: this deck should be played with Mecha Jaraxxus as Hero Skin; and you should emote before playing your combo, because LORD JARAXXUS COMMAND YOU TO DO SO!

EDIT:

Modified after Saviors of Uldum. Addedd a Zephrys the Great.