EDIT: Please follow the thread replies to see deckchanges.
Not the best removal but it is still removal. Very efficient vs northshire clerics, mana wyrms and similar cards, even shieldmastahs are a good target for this.
Ancient Watcher x2:
Keycard in your deck. It's used to combo with shadowflame to clear the board or serve as a powerful taunt with argus. Those guys are extremly viable and after using them in this deck I can hardly imagine playing without them again in any other decks. They are also fine to play in turn 2 if you don't happen to have anything to play.
Okayish removal, good for removing stuff like SSC's or Oozes and Knife Jugglers. Obviously there is better cards but we are playing control so we want this in our deck. In the lategame it can also be used on your infernals if you lack the 2 extra damage for the win.
Acidic Swamp Ooze x1:
This is mainly against paladins but it will help you against other weapon classes aswell. Sometimes it helps to pull an early watcher combo to not waste the second taunt of argus.
Big Game Hunter x1:
Not much to say, simply an awesome card to take out things like Ragnaros or the giants of mages. He's been the reason for a lot of wins.
Drain Life x2:
2 damage and 2 heal. Decent removal, you really need the heal against mages and aggression. Generally you want a lot of healing in the current metagame.
Earten Ring Farseer x2:
See above. Cheap minion and a heal ontop. Works really well, I would not replace him at all in this deck.
Shadow Bolt x2
Powerful removal, good against Azure Drakes and other 4 toughness minions. But you shouldn't be hesitant with sometimes overkilling weaker minions to play a bit more safe.
Defender of Argus x2:
Very important. Those guys go well with the infernals in the lategame, your ancient watchers or the giants. Even Ragnaros or Ysera. Yet I've often found myself using them earlier when the situation was dire.
Good card, you take damage but then this deck provides a lot of healing so this is not too much of a drawback. It has also been the killing blow several times already.
Sen'jin Shieldmastah x2:
One of the best taunts to defend against early pressure and overall one of the best taunts in the game.
Preferably you will want to use this on infernals or ancient watchers. Hellfire->Shadowflame->Hellfire will often make aggro players ragequit if you keep clearing their full board over and over again :D
Stormpike Commando x1:
This guy is a bit of a personal preference. Fire elemental is a powerful card and I view it kinda like a weaker fire elemental. You can take out 2-3 drops with it's battlecry or combo it with drain life/shadow bolt to take out bigger things. Basicly more removal while also giving you a bit more board control/baiting removal from the enemy.
Argent Commander x1:
Still one of the best cards even after the nerf. You could also drop something to get two of them.
Dread Infernal x1:
This is just something to force stuff like polymorph, hex, shadow word:death. It also helps you clear the board or get a kill sometimes but this card can easily be replaced with something else that suits you better.
Siphon Soul x1:
Removal+Heal. That's exactly what we are looking for. You should try to really save this for bigger threats but if the situation requires you might also just want to use it for the healing effect.
Ragnaros the Firelord:
He will give you the endgame punch you need, even if he gets removed he still often enough takes out something huge or does a big chunk of damage. He's also a powerful taunt together with argus.
This is what your endgame goal is. Once you get to jaraxxus and you have established some control over the board before you will most likely win the game. The healing effect is also very powerful. The infernals you spawn can trade with anything, can be used for shadowflame even as taunts. Very versatile while you bring the enemy down with your other taunts and weapon until he can't keep up anymore.
You will learn to love this card when you play this deck. Another heal is extremly good and the enemies pretty much never expect it to happen. I often save this for after Jaraxxus unless I'm forced to use it.
Mountain Giant x1:
Strong Minion to further establish your lategame. Sometimes you can get him out as soon as turn 4 altough it is not often the best thing to do against many classes.
Molten Giant x1:
This also works really well in a warlock deck where you constantly take damage from lifetap and small hits. Giants are simply good cards, ask our magefriends :D
How to play:
As mentioned. You want to drag the game out as long as possible. Trading 1 for 1 is perfectly fine since once it gets to the lategame you still end up with card advantage due to life tap. You also want to make the most of your argus defenders. When you arrive in the lategame you will begin taking control with 6:6 infernals from jaraxxus and 8:8 giants aswell as ragnaros.
What to do against mages?
You will easily outheal them. Keep the board clean early on, corruption on mana wyrms. Try saving your heals for when you get around 15 health or lower if you want to risk it. From there on you reset to 15 with Jaraxxus after taking fireballs or frostbolt+ice lance combos or pyroblast. If the mage keeps spamming spells into your face you will almost certainly still have farseers, drain life or alexstrasza to repeat that. Eventually the mage will have no control and no spells anymore and lose. Basicly it takes a bit of practice(and luck) to find a balance between living another turn and dying. You should however not use your heals when you are still at 18+ health. You can either do risks here and get a huge reward or get punished, you'll find your preference on when to heal after some games.
What to do against aggro locks?
Basicly try to remove as much and fast as you can, don't be scared of overkilling minions or trading inefficiently if that means you manage to get to the lategame where you can excel. Use heals like farseer early on.
Why do you only have 1 of a certain card/not use XY?
The reason for that is most likely I don't have more copies of the card or I don't have the card you'd suggest at all.
Why no Twisting Nether?
It is a powerful board clear but in the lategame you mostly want to(and) have something on the board before playing jaraxxus. To save you against earlygame pressure this card costs too much mana. Overall I never had a single game where I thought, damn I needed Twisting Nether but I can see it working if you want to use it.
Why no Soulfire of Succubus?
While those are great cards, in a control deck you want to be in control. Random discard is not my definition of being in control. Every single card you have is valueable and important, you don't want to discard any of them. In an agression deck it doesn't matter since you will get a new low cost minion to replace the other one but in this kinda deck every single card will be of use and important. I ran Soulfire when I made this deck first and I've had it often enough that it discarded one of the legendaries or giants.
Which cards would be replaceable in this deck?
Dread Infernal, Stormpike Commando. Acidic Swamp Ooze. Corruption? Maybe Demonfire or Argent Commander?
What cards could also be recommendable?
Sylvanas probably. An extra Siphon Soul. More Giants. Maybe another Big Game Hunter.
Anyways that's all I could think of. Feel free to give any feedback, criticism, suggestions or ask questions! I hope you will have as much fun playing this as I have!