Blizzard announced on Friday that they will be releasing a new adventure on Thursday, November 12th called The League of Explorers. This is a much quicker release than other adventures and expansions, which have taken up to a month for Blizzard to release after announcing.
The League of Explorers will introduce 45 new attainable cards through the adventure and class challenges, with a total of four wings for you to complete. It will cost $20 USD for the full adventure, or you can pay 700 gold/$6.99 per wing. The biggest addition in this adventure is the new mechanic, Discover. Whenever you trigger Discover, you will be able to choose one of three cards specified from Discover. Those cards can only be from your class or neutral cards. For example, Jeweled Scarab will trigger Discover off of Battlecry, and you will be able to choose one of three cards that cost three mana from your class or neutral cards.