There are new card backs, some changes to arena rewards and drafts, and a few bug fixes and changes, all of which you can see in the patch notes in this official blog post.
For fans of Blizzard's digital card game Hearthstone, if you're looking forward to getting your hands on the latest expansion, you'll be pleased to learn that Blizzard has announced that the Knights of the Frozen Throne expansion is now live and playable, which means that you'll just need to update your game and you'll be good to go.
According to the new changes, you will no longer receive duplicates of Legendary cards you already own.
In addition to 135 brand new cards spread across classes, the new expansions will bring us new game mechanics, including Lifesteal and Legendary Hero Cards that'll transform heroes into Death Knights.
Since I'm particularly keen on the Death Knight cards, which offer some fantastic-looking late game control options for nearly every class and almost all look to be quality cards, I made a decision to open my packs before going into the Adventure. Card packs can be purchased individually or in discounted bundles from the in-game Shop for gold or real-world currency at the same price as all other Hearthstone card packs.
Maybe that Lich King isn't such a bad fellow after all. This includes eight special Death Knight cards (shown first below), as well as the Warrior and Warlock Death Knights and their Hero Powers. Of course, it's highly unlikely the cards will all be unique, but at least you can start your adventure with some of the new cards in your decks.
Best of luck - I can only hope everyone gets as lucky I did with this launch.