The latest Hearthstone expansion is now live, and with it comes some very nice quests to help you get started into the expansion, a free copy of C'thun and two of his cultist buff cards, and also the new Standard/Wild format distinction.
Moving forward, we'll be getting a new season of cards each year that eliminates some of the older cards from being available. If you love your old decks, though, you can play in the Wild Format, but for those of you more interested in stepping into a new meta-game, Standard is the way to play.
This is a very similar thing to the way that Magic: The Gathering works - there Standard allows the latest Core Set and the last two expansion blocks. You'll still be able to play Wild if you want to have all of Hearthstone's history available for deck-building, but the idea here is to keep the game fresh by mixing up the meta-game, and allowing Blizzard to force out old overpowered strategies and cards without fully removing them from the game.
Notably, Hearthstone's Standard will always allow Classic and Basic cards, so the things that have been in-game since the game launched will always be available for play (though the recent patch nerfed and/or buffed a few of them to keep them in line.)
The current Standard excludes cards gained from the Naxxramas solo adventure and the Goblins and Gnomes expansion, but Classic/Basic card, Grand Tournament, Blackrock Mountain, League of Explorers, and of course the new Whispers of the Old Gods cards are all available.
To promote Standard, there will be a couple new quests that you'll get that reward several packs of Whispers of the Old Gods cards.
This expansion, I splurged and got the fifty-pack pre-order. It really shows you how rare Legendary cards are, as I only got two, and they were both Ragnaros the Lightlord - after opening all the packs, I managed to more than double the amount of crafting dust I had, which is considerable as I have crafted a grand total of two rare cards in all my time playing the game.
Given that C'thun is provided to all players, I naturally first created a C'thun-focused deck. While some C'thun cultists cards are class-specific, many are not, so I just dumped all the ones I had into the deck that fit with a Warlock and then picked out a few others that I liked.
One of my favorite new cards is Darkshire Councilor (maybe Councilmember or Councilman?) which is a Warlock card. It's 3 mana and is a 1/5 minion, but every time you summon a minion, he gets +1 attack. This is pretty great for any small-minion-heavy deck (it also triggers when minions are created by spells and effects,) and the 5-health body means he can actually fight a few times before he dies.
The C'thun cultists are often decent on their own, and I've won a few games without seeing C'thun at all. But there's something immensely satisfying about getting him out there after being pumped up to high health and blasting the crap out of the opponent's side of the table. If you have him, Brann Bronzebeard is a pretty fantastic complement to him, as many of the cultist cards buff C'thun with a Battlecry, and C'thun's burst of damage is also a Battlecry, meaning that with a 16/16 C'thun, you can wind up doing 32 points of damage when you drop him on the table. (And it's split damage, so Divine Shield minions are not going to have much of an advantage against him.)
Of course, the trick to any of the Old God-based decks is that getting up to 10 mana is going to require some finesse, not to mention drawing the card. There is a minion that will put a 10-cost minion from your deck into your hand if it survives a turn, which should help with this.
My strategy is largely using lots of taunt creatures and death rattle creatures that either buff fellow minions or generate additional minions to keep my board active. I can often survive long enough to cast C'thun if I get him into my hand.
While it feels like only yesterday that Goblins and Gnomes launched (or even was announced,) I'll say this: I am so happy not to have to deal with Doctor Boom or the freaking Healbot anymore. Priest decks are still a thing (and will probably continue to be,) but at least until people figure out the most annoying cards in this new expansion, I'm loving Standard as a format.
The new board is an Old-God corrupted version of the Stormwind board, which is sadly not terribly interactive (though I've been playing on my phone, so there might be more interesting stuff int he upper left and lower right that I'm missing.) I love the aesthetic of the expansion - the even-more-cartoony look of Hearthstone (as compared to WoW) helps transform the Lovecraftian horror of the Old Gods into something more Halloweeny and fun.
It shouldn't come as a surprise that the Old God cards themselves sort of demand to have a deck built around them. My own Warlock deck, "Cult of C'thun," feels awesome when it goes off well, but if I cast C'thun and either through bad luck or just not enough buffing by Cultists the match is not over (or over on the next turn,) the deck deflates really fast.
I haven't seen anyone play the other Old Gods, but it does look like there are a few "cultist" equivalents. N'zoth summons back dead Deathrattle cards, so obviously you'd want to have a bunch of those in your deck (sadly Baron Rivendare is no longer in Standard, as he'd be a pretty obvious piece for such a deck.) Yogg-Saron casts spells, and given the random nature of his spell fire-off, he's a bit of a gamble. Y'Shaarj summons your big minions, so I really see him working best in a Druid deck with lots of mana-gain and big, expensive minions.
The trick, of course, will be building decks that also work on an effective theme. My deck could use some work, as I think it does a decent job of building up to C'thun's summoning, but once I've pulled that trigger, there aren't really any rounds left in the gun.
I haven't seen or thought much about other themes to build around using Whispers of the Old Gods cards that don't include the OGs themselves, but I'm sure those will surface over time.