This is the third and final Tavern Brawl that accompanies the Fire Fest-E.V.I.L. event in Hearthstone. The way this Tavern Brawl works is quite simple: when you launch the mode for the first time, you get a premade deck.
You will then face a random opponent who also has a randomly drafted deck. In case of a victory, you will keep your deck while your opponent's one will be destroyed.
You can play this Tavern Brawl for numerous games, but you will only gain one Saviors of Uldum pack as a reward for your first victory.