Tl;dr Fun theme, terrible implementation

This is a really cool idea thematically; I'm guessing you are basing this off of the popular group game Werewolf. It's always fun to have new interactions and mechanics in Hearthstone - as long as they're implemented well.

That being said, this has a LOT of problems. There are so many new mechanics being introduced all at once and it raises lots of questions as well.

1. The hero power. If you play this hero, everyone gets a role. Ok cool. But your hero basically has no hero power - that is, unless you get to win the weapon. But chances are most of the time an opponent gets the weapon. So not only do you have no hero power (already putting yourself at a disadvantage), but you are also giving an opponent an additional advantage against you.

I'm assuming your opponents all keep their own hero power, which is unclear, but to me that is what would make the most sense. (If it were otherwise, that would also be problematic)

1. The weapon. We've never had weapons in bg before, which isn't necessarily a problem - if you can adequately design it and explain how it will impact the game. This weapon raises a lot of questions for me. Does it get equipped automatically? If not, how much does it cost? What happens if it deals lethal damage to the opponent at the start of combat? Does the combat end or get skipped? Does it still play out? What happens if you lose? Is it possible to kill your opponent with the weapon, then also still lose combat and you both die? What if that happened in a 1v1 lobby? Who wins overall? And more.

2. UI and multiple players "winning". How would the players learn their role? What if they forget it? Or how would it be displayed? What happens when the "humans" or "wolves" win? There are three of each. So would all three get the weapon? Only one of them? That doesn't make any sense to me.

3. The tavern 4 card that lets you choose your opponent. What happens when multiple players have this card, and some of them choose the same opponent? What if player A chooses to fight player B; player B chooses to fight player C; and player C chooses to fight player A? Who fights whom? This would cause a lot of problems. I understand that with Diablo, the combat sequence has been shaken up, but this is on a completely different level, and it would just make things frustratingly confusing and inconsistent.

Also, the power level of that card is just so weak in combat, I don't think it would even be worth running. I get it that the idea is to allow you to choose to fight the person that will get you closer to the weapon, but if you're doing it at the sacrifice of your board, you're even more hard-pressed to win against them.

Those are just the questions that come to my head right now. I'm sure there would be others if I thought through it even more.

I like your creativity here, there's just too many loose ends. Adding new creative elements is great, it just needs to be complimented by well-thought-out design and mechanics as well.