http://www.pcgamer.com/hearthstone-heads-underground-in-december-with-the-kobolds-catacombs-expansion/

Generally speaking I make it a rule to avoid caves, particularly if they're already occupied, as the only loot you're likely to find are syringes and brandy bottles. But I'm willing to make an exception for Kobolds & Catacombs, the underground-themed expansion for Hearthstone which was announced today at BlizzCon. As expected, this is another full-size set, meaning 135 new cards will be added to the Standard and Wild pool when it launches sometime in December.