“Heroic Brawl will challenge even Hearthstone’s most experienced players as they vie for glory and in-game rewards! Participants will create a Standard deck from their existing card pool and lock it in before their first Heroic Brawl match. No changes can be made to your Heroic Brawl deck once you’ve locked it in, so be sure to do a bit of testing before you finalize your deck. Once you’ve locked in your Standard deck for Heroic Brawl, you’ll be pitted against other Heroic Brawlers in heated battle. Just like the Arena, you want to shoot for 12 wins to get the best rewards—but if you get three losses, you’re out!”
Players so far seem more opposed to the idea that it replaces the free event than that it’s available at a cost for those who do want it, although rest assured there’s plenty of concern that Blizzard is venturing down an uncomfortable monetization path. TouchArcade has also pointed out that while it’s a relatively expensive event, the rewards are commensurately generous.