http://www.pcgamer.com/hearthstone-kobolds-catacombs-is-live-in-north-america-and-europe/

The Hearthstone expansion Kobolds & Catacombs was slated to go live later today in North America, and not until tomorrow in Europe. Here's an early holiday surprise, then—Blizzard says it's live in both regions now. 

Kobolds & Catacombs brings 135 new cards to the game, but our expert recently picked give that might be sleeper hits: Lesser Mithril and Lesser Emerald Spellstones, Spiteful Summoner, Arcane Tyrant, and Temporus—could be the next big thing in Hearthstone. But this one—Duskbreaker, a 4 mana 3/3 Dragon—definitely will be.