Blizzard has initiated a legal battle with Chinese game studio Unico Interactive over a copycat Hearthstone game called Sleeping Dragon: Heroes of the Three Kingdoms. While their titles may be entirely different, the games are remarkably similar.
Aside from the shared aesthetics (to put it lightly) with Hearthstone, Sleeping Dragon also takes musical inspiration from other Blizzard games -- namely World of Warcraft. Yes, Unico's card game actually lifts its tunes from Blizzard's MMO.
Here's a screenshot of Sleeping Dragon, by the way:
Hilariously enough, Sleeping Dragon's publisher, The9, was at one time the World of Warcraft distributor in China. This was before those rights were taken, and the company has been sued multiple times before over copyright violations by other parties.
Either way, Blizzard and NetEase, the current World of Warcraft publisher in China, are suing Unico for 10 million yuan (about $1.65 million USD) over copyright infringement. The9 is not, at the moment, included in the case.
Blizzard's popular card game recently entered open beta in North America.