We're getting some new adventure content in Hearthstone starting this month on September 15 with Jaina Proudmoore.

Initially, we'll only be able to run through Jaina's campaign but more classes will be added over the next 12 months until all the stories of our core heroes have been told.

  • The content is completely free to play.
  • You'll earn a Mage card pack which contains Standard Mage cards for defeating all 8 bosses.

We datamined Scholar Jaina not too long ago so it looks like this is where she came from! The hero will be purchasable starting on September 15 in a special bundle.

Quote From Blizzard

Follow Jaina Proudmoore’s journey from scholar to mighty Mage in Hearthstone Book of Heroes, an all-new solo experience! Hearthstone Book of Heroes will bring fresh and FREE single player content over the course of the next 12 months, until the stories for all 10 core Heroes have been told. Defeating all 8 bosses in this linear adventure will reward 1 Mage Pack, containing only Mage cards from Standard!