Blizzard's plans for the coming year in Hearthstone includes a new RPG-like mode called Mercenaries. It lets you assemble a team of fan-favorite characters and level them up to unlock new powers and abilities. It's coming later this year.

The Mercenaries mode will include both PvE and PvP modes. In PvE, you'll take on a gauntlet of randomly generated encounters, which grant you loot and experience for unlocking more powerful versions of your heroes as you make your way to the final boss. In PvP, you'll come to blows with an opposing Mercenary team, and you'll each plan your next turn simultaneously--a sharp departure from the standard turn-based combat in Hearthstone.

The announcement specifically mentions Sylvanas Windrunner and Ragnaros the Firelord as examples of heroes who will be recruitable in Mercenaries. The new expansion, Forged in the Barrens, will introduce 10 legendary mercenary characters as part of a new year-long storyline, so it seems like a safe bet that they'll be involved in the new mode as well.