Boss #3: Chromaggus

Though he looks almost like a Cerberus-style, multi-headed dog-type creature, Chromaggus is actually a mutated dragon beast created by Nefarian's experiments. Within this creature rests the power of all five of World of Warcraft's dragonflights, and those powers manifest as five different powerful debuffs that a brave raiding party must learn how to deal with.

"To me, that's the core experience of that fight — dealing with these different debuffs based on all the different dragonflights," Brode says. "I'd been thinking for a while about the idea of cards that can trigger while they're in your hand or basically act as debuffs while they're in your hand. I felt like Chromaggus was a good opportunity to do this."

In his Hearthstone form, Chromaggus will summon a special Brood Affliction card into the player's hand every turn. The effects of these cards range from damaging the hero to healing up Chromaggus, to making his minions cost less to summon. These cards will remain active as long as they're in your hand, but players can choose to get rid of them at the cost of one mana each.

"This is one of the most unique fights in Blackrock Mountain," says Brode. "Do you want to spend the mana to dispel yourself? Or would you rather spend the mana to play your normal minions and spells? It's a design space that we haven't really done anything else with except these adventure cards."

The Hearthstone team plans to carefully monitor how players react to the Chromaggus fight to see if these kind of debuff cards might be something they want to explore more in the future, possibly through cards players can use against each other. But it will require balancing, just as the Chromaggus fight did.

"These went through a lot of iterations," he says. "They're pretty complicated, and there's nothing else really like it, so it was hard to figure out whether it was fun to play against and cool and understandable."

In one earlier form of the Chromaggus fight, the cards acted more as debuffs to the player hero rather than buffs to Chromaggus — making minions cost more and such. According to Brode, this version of the fight ended up feeling "too stifling."

There was one other form of the Chromaggus fight that almost happened. In the World of Warcraft fight, he can actually turn people into chromatic dragonkin. This aspect almost made its way to Hearthstone as well.

"We had a version where he would turn the player into a chromatic dragonkin, and your hero power became really bad," Brode says. "It was one mana to discard a random card. But it turns out that against Chromaggus, you have a lot of cards in your hand you don't want, because they're hurting you. The afflictions cost a little bit more to get rid of in that world too, so it was a cheap way to get a chance at dumping them."

In the end, Brode decided to stick with focusing on just the debuffs. "It was a little too complicated when we were turning players into different things," he says. "It got more and more fun over time."