Blizzard announced at Blizzcon 17 the next expansion for Hearthstone titled Kobolds and Catacombs and ahead of its release are giving away a free card.
From now on when you login to the game you will be awarded with Marin the Fox. This card is part of the expansion due in December but Blizzard have released it now to get players excited. The card has a battlecry that when played will summon a 0/8 treasure chest on your opponents side of the field. If you can then break open that chest you will be rewarded with some awesome loot. On top of that but Marin is also a 6/6 with a summon cost of 8.
Hearthstone: Kobolds and Catacombs is set to release sometime next month.