While this might come as a bit of a surprise, especially for those of you that bought it at launch, Diablo is currently celebrating its 20th anniversary! And given how it not only revolutionized the hack and slash genre, but also created its very own, it shouldn't come as much of a surprise to hear that Blizzard has something special planned in order to commemorate this anniversary.
In Hearthstone's case this means a brand new Tavern Brawl, along with a time-limited and Diablo themed card back. So if you're up for infusing your game with the slightest touch of hellfire, now would be the time to do so as the Dark Wanderer Tavern Brawl will only stay active for a few more days. And if you're worried you might not have the cards necessary to defeat Diablo himself, worry not as he seems to be quite inept at card games.
The duel itself is fairly straightforward, and if you're even remotely awake you should be able to stomp all over Diablo. However, simply beating the Dark Wanderer is not the goal of this Tavern Brawl, instead it is his secrets that you need to defeat. If you manage to activate all three secrets, an act that will most likely take you multiple attempts given that they are pulled from a pile of newly created ones, you'll be granted access to the greatest 'secret' in all of Diablo - the dreaded Cow Level!
And before you ask, no, you don't actually gain anything for defeating the Cow King. Its purely there as a little bit of an Easter egg, so if you don't feel like jumping through hoops in order to get to the Cow Level you can just check it out on Youtube instead. But if you do decide to try your hand, I wish you the best of luck as some of the secret combinations are downright evil!