So far, Hearthstone’s alternate heroes have required a cash purchase. The newest hero, the paladin Lady Liadrin, will unlock in a different manner as Blizzard tries to create some cross-game synergy with its “other” big game.
To unlock Liadrin, you simply have to possess a level 20 character in World of Warcraft. After logging into your WoW account, you’ll receive an achievement, Fledgling Hero of Warcraft, which will then unlock the alternate hero in Hearthstone. Since WoW is free to play up to level 20, this means you don’t have to purchase the game or have a subscription to unlock Liadrin. You can snag the full details on Lady Liadrin on the Hearthstone website.
I don’t want to read too much into this promotion, but it’s worth noting that previous Hearthstone/World of Warcraft interactions have tried to steer players from WoW to HS. With Hearthstone still going strong and WoW subscriber numbers tumbling, it’s interesting to see Blizzard trying to go in the other direction.