Hearthstone‘s newest solo adventure, Tomb of Terrors, debuts today. Hearthstone became the king of the digital card game world thanks to its multiplayer offerings, but the free-to-play Blizzard Entertainment game has found a successful format for single-player content that has players making their own decks as they fight computer-controlled bosses. One loss and you have to start over, similar to roguelikes.

This kind of solo experience started when Dungeon Run came out with the Kobolds & Catacombs expansion in December 2017. Since then, every expansion has added some kind of new spin of this mode. Now Tomb of Terrors looks to delight solo players by focusing on some of the game’s most popular characters, The League of Explorers.

I had a chance to talk with three of Hearthstone’s developers — lead missions designer Dave Kosak, game designer Alec Dawson, and lead game designer Mike Donais — about their approach for Tomb of Terrors and what sets it apart from its predecessors. This is an edited transcript of our interview.

GamesBeat: How did you make Tombs of Terror different from all the other solo modes you’ve done?

Dave Kosak: We wanted to keep the same core experience, because we think that building a deck as you run through a dungeon is a really fun form of gameplay. But we wanted to mix it up in ways that made sense for The League of Explorers. There are three big changes in this mode from previous ones. The first is that the heroes are dual class. That gives you a lot of fun deck building options. You can build combos that you’ve never been able to play with in Hearthstone before. That right away makes it feel pretty different. All the buckets of cards you’re choosing from have both classes together. It’s a lot of fun.

The second big change is we have what we call “signature treasures.” These are treasures based around your hero, and there are six for each hero. You pick one to put in your starting deck. What’s nice about these is, they unlock over time as you play the game, so it gives you a nice sense of progression. Some of those signature treasures are extremely powerful, and they tell the story about how The League of Explorers gets from where we last saw them to where they are in the Saviors of Uldum. You can see them discover the treasures that make them who they are in the Saviors of Uldum expansion.

The third big difference is we changed up the final bosses. In previous Dungeon Run iterations, the final boss was always the hardest one. You either beat this really tough fight, or you lost, and you were out. This time around, the final bosses are these huge, gigantic monsters that have persistent heath. They have like 300 health. They are the Plague Lords that you have to fight. You can damage their health over time. The first time you encounter a Plague Lord, you can do some damage, and if you lose the fight there, that damage is saved. The next time you encounter a Plague Lord, you can chip away at it over multiple encounters. Those three changes, it creates quite a different feel. You get to play with these characters, the dual class characters. You get to gradually unlock their full power over time. You have really big final bosses to fight. You have to go after them multiple times. It creates a really different experience.

GamesBeat: What happens when you defeat one of these Plague Lords? Does its health reset the next time you do a run with that character?

Kosak: Yeah, they’ll reset. You’ll have completed that chapter, and you get the nice chapter completion reward. Then it resets, so you can tackle it again.

Mike Donais: There’s another thing we did. Once you beat a Plague Lord, to make it even more replayable, we make it so that more monsters infest that wing.

GamesBeat: Kind of like a Hard Mode?

Kosak: One of the things we did in previous adventures is, for instance in Dalaran Heist, there was a shared pool of bosses between all the wings. But often you would unlock a new wing and you’d see some of the same bosses you fought before. We wanted to give you a different experience, so we have all the unique bosses for each of the wings. When you defeat that wing, though, all those monsters get unleashed into the shared pool, and then they start to infest the other wings as well. Once you’ve played the mode for a while, the bosses all spread out. It gives you the maximum variety. But every time you unlock a new chapter you’re guaranteed to see new bosses.

GamesBeat: How did you decide which classes would belong to which explorer?

Alec Dawson: Going back, when we were first talking about this, Reno is one of the characters we planned on first. Mage and Rogue. He steals powerful artifacts that give him power to become a mage. If you look at Reno in Uldum, he’s in the Mage class because he’s stolen that power. He’s acquired it. He can take some big disadvantages sometimes. A little bit on that, actually — back in Rise of Shadows, we played with this idea of dual-class heroes. Which classes would be attributed to which heroes? Just looking at all of them as a whole. When we got to picking two with The League of Explorers, we had sort of gotten this a bit. We knew which heroes we wanted to attribute to who, and which class pairings made a lot of sense and were a lot of fun, if you could pull from both pools of cards.

Above: Reno and Finley.

Image Credit: Blizzard

GamesBeat: Dungeon Run has become the model for these solo modes. Was there any idea that that mode would be so influential on Hearthstone’s development? 

Dawson: Early on — I often tell this story. We had a really janky early playtest of the Dungeon Run. It didn’t have any interface. It just all took place on one battlefield, and every time you defeated a boss, it just reshuffled the deck and put a new boss in there. That was how we tested it. Even with that really hacked implementation of the idea, it was so much fun. We knew we were on to something really early. When we released the original Dungeon Run in Kobolds and Catacombs, we thought it would be a lot of fun. We thought it would be popular. But it turned out to be immensely popular for new and returning players as a way of playing Hearthstone. We really wanted to flesh out and explore that idea, because it was a great way to bring in new players and to keep players engaged with the game. We’ve been playing with the idea quite a bit. It’s even more popular, probably, than we anticipated, but we’ve been having a ton of fun with it.

GamesBeat: You’ve been doing a new solo mode for each expansion since then. Has it been challenging to think of a spin on the formula every time? 

Dawson: Yeah. We’ll often play around with ideas, and if they’re not quite right, we push them on to another one. Sometimes we have a little pool of idea that we’ve been playing around with that we were finally able to implement. In The Witchwood, we were originally going to experiment with dual-class heroes, and then ultimately we ended up just giving them crazy hero powers instead. In the very original Dungeon Run, we played with the idea of unlocking different hero powers, and it wasn’t quite working for us then. We eventually did that in Dalaran. We do have lots of ideas for what to do with this mode, and we’re always trying to figure out what makes the most sense story-wise with what’s going on in each expansion.

A story of heroes

GamesBeat: The League of Explorers are these really popular characters now. Is it fun to bring them back and build a whole mode around such a beloved cast?

Dawson: Our original plan — you remember the card Zephrys, that grants you a wish for the perfect card? We were originally going to have that be the host of the adventure. They would be the narrator introducing you to this and walking you through picking your cards and everything. What we found as we started to write the VO is we had so much fun with the explorers, and the explorers bantering back and forth — Reno would talk to Finley, or Brann has an argument with Elise — that was so much more compelling. We really wanted to focus on those characters. We ended up scrapping a lot of the Zephrys VO and really just focusing on these four characters and their banter back and forth. I hope we captured some of that in the cinematic that was released last week, the Tombs of Terror cinematic.

They’re so much fun to play with that we ended up really focusing on them for all of the VO and the dialogue. We have great moments every time you start a new chapter with a different character. There’s a little exchange as they talk about what they’re doing in that chapter with the other heroes. We ended up having a lot of fun with it. I think part of the story of Citadel of Doom and Tombs of Terror is The League of Explorers leveling up. We get to support that space with cards and mechanics and new hero powers. That’s something we’ve wanted to dive deep into. Getting these characters back with dual classes and all the new hero powers they’ve acquired is something we’ve had a ton of fun with.

Hearthstone: Saviors of Uldum.

Above: The League is ready.

Image Credit: Blizzard

GamesBeat: You get to make new cards for these modes that are only available in the solo mode. Is it extra fun to make cards where maybe you don’t necessarily need to worry about breaking the competitive game? 

Dawson: It does give you lots of design freedom. It’s interesting. Some spaces are open. You can do mean things to the AI that we would never let you do to another player, because it would be a really frustrating play experience. But the AI doesn’t care. We can abuse it in interesting ways. You need to find cards that break the rules, but they break the rules in an interesting way that’s going to be a lot of fun to play with. There are, I think, 28 new active treasures in this mode. We brainstormed a lot of ideas. We also try to find that space of letting you do weird things to the game of Hearthstone that are a lot of fun to play with.

GamesBeat: This mode is coming out a bit after a launch of the Saviors of Uldum expansion. How does that delay impact development?

Dawson: We’ve found that when we released Kobolds & Catacombs, it came out alongside of the PvP set. That really divided our player base. You sort of had to sacrifice some of the most exciting time on the ranked mode in order to play the single-player there. It felt a lot better if we gave the sat a little bit of breathing room. You have the period you’re in right now, where people can play the collectible set and experiment with a lot of different builds. Then, a month in, five weeks in, the single-player is available. That helps spread out the excitement a lot better. On the development end, it was great for the previous set, because we had an extra month of development time. It was a one-time extra month, and now we’re sort of on the same schedule again. Just shifted by a month. It’s tricky. There’s quite a bit of adventure content. There’s tons of content in here. It’s a lot to get done in the four months that we have with each expansion.