Hearthpwn

Mechathun Druid is the budget Hearthstone deck I have been playing this week and I have to say I personally think that it is pretty good. It is like the only good Druid deck in the meta right now and to be quite honest I think that it severely underrated. The main goal of this deck is to play a ton of cheap spells to synergize with Wild Pyromancer/Acolyte of Pain, and the Gadgetzan Auctioneer in order to draw through your deck in a matter of like 9 to 10 turns. Additionally, you have ferocious howl, branching paths, and oaken summons for a TON of armor and some added cycle as well. The deck is hard to kill and has decent removal options and board wipe with the pyromancer and spellstones and naturalize and even Wrath.

Mulligans:
Basically, you want to get rid of all non-draw cards early and kinda expensive spells so that way you can use them early on to cycle the deck and get them out of the way so you don't have them at the end of the game and stall out for a turn or 2. So Ferocious Howl and branching paths are good choices and oaken summons can be as well but has a chance of dragging out a minion you don't want.

Aggro: Keeping a pyromancer, a spellstone, or a wrath to deal with early threats. Other than that just a ton of armor.

Control: You don't need removal you need things that can combo with an Auctioneer or the Pyromancer/Acolyte of Pain combo to draw cards to basically draw spells, cheap spells for combos, and the auctioneer (the other guys you can bring out with oaken summons so you don't need them as bad and will combo later into the game as well. That being said, if you have the combo in your opining hand you can keep it but if you only have like 1 or the other you can go for something better.

Gameplay:

Guide: