Hearthpwn

This deck felt the most solid on my climb to Legend in the first month of Boomsday.  It's fairly versatile in that it can apply a lot of pressure in the midgame vs control decks with Mountain Giants, while also having removal options for aggro decks.  It's also a consistent deck because you usually have a full hand.  In most games, you will be able to play a Mountain Giant or Twilight Drake by turn 4.

The main thing Boomsday brings to the table is the tech card Demonic Project (which is the only reason why Sacrificial Pact is in the deck); it helps versus one of its worst matchups: combo OTK decks (e.g. Malygos Druid and Shudderwock).  This makes the deck even scarier because it doesn't have an oppressively bad matchup anymore.  Currently the worst matchups are big-spell mage (which are rare these days) and hyperaggressive decks that hit face a lot, such as Odd Rogue and Secret Mage, but we have Acidic Swamp Ooze to help out.

I will go over each matchup below in order of how common it is.

 

vs Warlock (Assuming Mirror Match)

Keep Mountain Giant unless you are certain it is zoo.  If you have Mountain Giant and you know it's a mirror match, keep Bloodreaver Gul'dan.  If the game isn't over by turn 10, usually whoever plays Bloodreaver Gul'dan first usually wins.

Toss Twilight Drake unless you already have Mountain Giant.  Mountain Giant is too critical in the mirror.  It is extremely hard to deal with on turn 3 or 4 unless you have your own, and if you play it first, you have a huge advantage, since you can hit face with it and become the aggressor.  This puts your opponent on the backfood and forces him to answer your threats for the rest of the game.

Keep Doomsayer if you are going first.  They can play Mountain Giant on turn 3, so you will want to Doomsayer on 3 then play your own giant on turn 4.  If you are going 2nd AND you have Mountain Giant in hand, toss this card.

Obviously if you know it's zoo then keep Hellfire / Defile.  But our deck is already favored against zoo so if it's unknown I mulligan against the mirror.

 

vs Druid (Assuming Malygos)

Keep Skulking Geist, Mountain Giant, Twilight Drake.

Geist is king in this matchup.  This one card destroys almost all of their removal.  Assume they have Naturalize for your Mountain Giant, so don't overtap to play it (e.g. on turn 4, if the giant costs 4 mana, don't tap and make it 3).

Play Doomsayer if you can't play drake/giant and they are going into 5 mana.  You don't want them to get ahead of you on board with Nourish and Arcane Tyrant.  Usually this happens on turn 3 when you are going first and they played Wild Growth on 2.

Play Demonic Project when you think they have Malygos in hand.  I usually play it late in the game in the game after they've aggressively drawn some cards.

Once they play Alexstrasza healing becomes very important because they can aggro you down with the Malfurion hero power, so try to protect your face as much as you can after that point, and limit tapping.  The struggle is that you'll also want to find Bloodreaver Gul'dan as soon as possible so you can get health back.  You are generally safe at 13+ hp, but this is where you need to look at how many Swipes / Moonfires have been used and count how much damage he can deal in 1 turn.  If he hasn't used any Swipes be sure to stay above 8 hp, etc.  Even if you Demonic Project his Malygos, you can still die from this position so don't get cocky!

 

vs Hunter (Assuming Egg Hunter)

Keep Spellbreaker, Skulking Geist, Mountain Giant, Twilight Drake.

Spellbreaker is the most important card to have on Turn 4.  Usually they play Devilsaur Egg on turn 3, then follow up with Terrorscale Stalker.  Skulking Geist is also very important.  Destroying Play Dead, Hunter's Mark, AND Tracking is a huge win.  The matchup isn't that aggressive so you can afford to keep these tech cards.

 

vs Rogue (Assuming Odd/Aggro)

Keep Doomsayer, Hellfire, Lesser Amethyst Spellstone, Acidic Swamp Ooze, Defile.

If you don't draw any healing cards, you will probably lose the matchup. Hellfire > Defile because nothing in your deck has 1 hp and nothing he plays early on will have 1 hp.

If you're going first you can hold off Doomsayering until turn 3.  You just want to play it before they get 3 mana to play Hench-Clan Thug, but usually they play dagger on 2 to buff it.  Assuming a standard opener of 1 drop + dagger, a 2 card combination of Cold Blood, Deadly Poison, or Southsea Deckhand is required to kill the Doomsayer, which is very unlikely because rogue doesn't keep any of those cards in the mulligan (except maybe Cold Blood if they drew the nuts already).  It's a tiny but worthy risk IMO.

 

vs Warrior (Assuming Odd/Control Warrior)

Keep Bloodreaver Gul'dan, Skulking Geist, Mountain Giant, Twilight Drake.

This game will most likely end in fatigue.  Start aggressively with the standard Mountain Giant / Twilight Drake opener.  Sometimes you can win early but if it doesn't work, slow down on Life Tap because the game will end in fatigue.  When you play the Bloodreaver Gul'dan try to suck face as much as you can.  They don't have many threats and you want to put him on the backfoot dealing with your threats while slowly chipping away at his health.  When it gets to fatigue you will be thankful for all the health you chipped away.  If you have less cards in deck than him, consider saving some healing towards the end.  The DK will generally keep your HP at max, so it's important not to overheal.

 

vs Priest (Assuming Topsy Turvy combo)

Keep Mountain Giant, Twilight Drake.  Keep Sunfury Protector if you have giant or drake.

They usually don't play Inner Fire anymore so Skulking Geist isn't necessary to keep.  A well timed Sunfury Protector usually leads to them conceding.  Be sure to kill the high health minions.

 

vs Paladin (Assuming Odd/Aggro)

Keep Doomsayer, Defile, Hellfire.

Defile > Hellfire, because, you know, their hero power activates Defile.  This matchup is pretty easy, just keep their board clear.  Try to save AOE if you can.  You don't really have to go balls to the wall with the board clears until he's going into turn 5 (to prevent Level Up! and Fungalmancer).

 

vs Mage (Control)

Keep Mountain Giant x2, Twilight Drake.  Keep Bloodreaver Gul'dan if you already have a Mountain Giant.

The only way to win this matchup is to aggro them down before they play Frost Lich Jaina.  Mulligan aggressively for Mountain Giants and hope they don't have answers for it.

vs Mage (Secret)

Keep Doomsayer, Hellfire, Lesser Amethyst Spellstone, Defile.

Just try to survive and play around secrets.  It's usually just 1x Counterspell and 2x Explosive Runes.  It's the worst matchup so good luck.

Mages are pretty rare these days but both matchups are the worst for this deck.  What's even worse is the mulligans are polar opposites.  So if you lose don't sweat too much and move on.  If mage becomes more popular then this deck will be not as good.

 

vs Shaman – Is that a new class?