Baba Yaga
Well, you've done it. The journey was fraught with peril, and darkness, and despair, and porridge. But you've made it all the way through your journey with just a little bit of help from that friendly merchant along the way. Wait, who was that, anyway? 

Turns out your "friendly merchant" was actually the powerful Baba Yaga, just keeping an eye on your progress to make sure you aren't too much of a threat to her own iron-fisted (and chicken-footed) grasp on the Tanglewoods. And, as it happens, you are! 

Play with all three decks! 

This campaign mini-expansion allows you to play all three decks (in any order) with additional challenges thrown at you by the Baba Yaga. Each deck will have new minions sent from the witch herself to impede your progress. Avoiding them might be prudent, but if you don't fight them now, then they'll be at Baba Yaga's side later. Additionally, defeating them now will help speed your progress along. 

Do well, and you'll carry powerful bonuses from one game into the next. If you struggle, you might lose some of your progress and some of your upgrades as a cost to stay in the game. If you manage to work your way through all three modified decks, you'll have Baba Yaga herself waiting for you at the ened as a reward for your hard work. And as boss encounters go, this one is no cake walk...