Eight years is a long period of time, and Hearthstone hasn’t stopped increasing its decks in that span. With over 20 expansions and adventures released since its 2014 launch, there is no shortage of cards to parse through and experiment with. But when these additions arrive with over a hundred cards in the existing mix, iterating and balancing this ever-increasing pool becomes a tricky process.

Game Developer sat down to talk to game designer Leo Robles Gonzalez and lead VFX artist Dominic Camuglia at Blizzard about what comes into the creation of a card, how much iteration and theming can define the final deck that players get in their hands, and the philosophy around adding a second resource to Hearthstone with the March of the Lich King expansion.

A thematic foundation

Once the teams decide on the theme of an expansion, the exploration period begins. This includes design for mechanics, testing ideas that work as well as some that don’t, and fine-tuning the ones that make the cut. After that phase, the focus shifts to individual cards and classes.

“That’s when we start saying alright, Shamans, we’re giving them shadow spells, because they’re evil and part of the Scourge now,” says Gonzalez. With that theming in mind, the development team starts to delve into what that will mean for the cards, and how they’re going to behave. “That phase of just individual card design and iterating on the identity of the classes and the balance—how much mana should this cost, how much damage should it do—that takes a while.”

It’s around halfway through the main design process when other teams start getting looped in. The first half encompasses aspects like the first art wave where the devs write card descriptions and then send them out to artists. The second half involves Camuglia’s team, as well as voiceover recordings, final balancing for numbers, and so on.

“Halfway through the design process, we have meetings where VFX, engineers, and other teams get to review the list and see if there is anything that we need to budget more time for, or needs a particularly expensive effect, and whether or not that’s possible,” says Camuglia. “By the time the card is mostly solid, it comes to my team, we take a look at the illustration if it's done yet, what the art description is, what design has in mind for the flavor and the character, and then we start building up the effect.”

The VFX team ensures that every effect has the desired result—whether that be striking imagery or a reference to the theme itself—and also communicates the card’s properties intuitively. This process can take one or two weeks, and it leads to back-and-forth feedback between the design and effects teams from there. Once all parties are satisfied with how the card turned out, it is then passed along to the audio team.

Hands on deck

Of course, each theme comes with its own particularities that can shape the game in different ways. Deciding the core and secondary characters, which cards will need more time to work on, as well as how the theme affects everything that already exists in the Hearthstone universe are just a few iteration points.

For March of the Lich King, the one sentence pitch is "Lich King [is] rising armies of undead to fight the Blood Elves." With that settled, the team moves to look at all the classes and put them on different sides. “We ended up putting a ton of stuff where we thought it made sense,” says Gonzalez. “I think Hunter was clear [from the start] because Blood Elves have the Farstriders, which are like the very elite rank of hunters, so that made sense.

Some classes weren't super clear. I think Druid is one we kinda went back and forth a lot on. The Blood Elves of Silvermoon don't really feel super Druid-y, but also the Scourge doesn't feel super Druid-y. But I think the decision was informed very well by concept art we got back where someone did art of a beetle forsaken Druid wearing scarab armor and we were like that's awesome, we're doing that, beetles.”

Gonzalez adds that every designer works differently. In his case, he tends to look at inspiration from World of Warcraft, as well as other sources, to figure out what can work within the context of the universe as a whole, not just in Hearthstone.

Deciding that the Shaman would be part of the Scourge was the first step, but there had to be a plan regarding how Undead Shamans would look and feel. As such, the idea of forcing Shadow Magic into their kit and figuring out what that entails became the starting point. “I think characters can inspire designs, designs can inspire characters, it’s really a mixed bag,” he says. “But as long as it feels at home in the set and doesn't feel out of place, I think we're doing a good job.”

Inevitably, some cards end up requiring more attention than others, whether they involve a character that’s central to the expansion’s theme or plot, or because of their pre-existing renown in World of Warcraft. For the Death Knight class, the Corpse Explosion ability in WoW —which does exactly what the name advertises—was a card that designers were excited to work on and experiment with in different ways.

“Death Knight is a good example,” says Camuglia, “as most of the time we do unique effects for legendaries, but for Death Knight we needed to make a whole palette of what the effects kit of the class looks like. So a lot of that we had to build up from scratch because, we’ve done Frost before, but how does Death Knight Frost looks different? Like Corpse Explosion, we haven’t done a lot of blood effects in Hearthstone at all, so building that from the ground up was really exciting. Corpse Explosion is kind of the culmination of what we’re planning for that school of magic as a whole.”

The Death Knight is a new class in Hearthstone, and alongside the new cards, it also introduces the Runes mechanic. In summary, the player can opt to use up to three runes corresponding to different schools of magic or combine them: Blood, Unholy, and Frost. This ultimately defines which cards you will be able to have in your deck, as each has its own requirements. Deciding which ones to prioritize on the VFX side of things was also a tricky process.

“On top of doing all the effects of Death Knight we also had to do all the legendaries,” says Camuglia. “There wasn't a ton of time that we could budget for it, so I wanted to make sure that we were working smart.” Studying the common themes between the cards, and how the team wanted to communicate the themes with a set playstyle helped to decide how they would behave.

In some cases, some of the effects could be reused in other cards, modifying the intensity. “A lot of them, like Icy Touch for example, it's a simple direct damage, we can reuse that across different things and make different intensities of Frost magic that does damage. We knew we didn't need to spend too much more time on that compared to a lot of the more 'special' triple Rune cards,” he says.

Balancing the stakes

Finding the right spot in terms of balance for Hearthstone before adding dozens of cards with each expansion is no easy task. As Gonzalez explains, the number one goal with every expansion is to ensure that they’re making new, engaging additions—balance, however, comes next on the to-do list. The Death Knight class in particular took a long time, and some designers started working on ideas before everybody else. It was during that search that the concept of Runes came to be.

“Death Knights can do a lot of different stuff, we wanted them to be super powerful, and be able to control the undead in a variety of different ways,” says Gonzalez. “The problem there that comes up is, if they can do almost everything, what are they bad at, right? If they can fill the board, if they can increase their health, where is their weakness? And the answer was the whole Runes system.”

For example, players who focus on Blood Runes can increase their health up to 60 HP, but that focus leaves them out of the possibilities of Frost damage or swarming your side of the board with an undead army with Unholy cards. This helped keep the Death Knight in check, since players are unable to just run the best card out of each school of magic into one single deck.

The team was deliberate in its choice to make March of the Lich King as complex as possible, coming up with a class that would take time for players to learn and master. “There's a lot to experiment with Death Knight, and I think for newer players it can be a little bit overwhelming,” says Gonzalez. “But my recommendation is, find the card that you think it's the coolest or the flashiest. If you wanna play Vampiric Blood, because you wanna get to 60 health, throw that in your deck, and that has 3 Blood Runes. Now you know what type of Death Knight to build.”

While some designers were looking into the new class before everyone else, Hearthstone's expansion team has two sub-teams. The first handles the initial design, responding to questions such as what the fantasy of the expansion is and what the classes are doing. They focus on the big picture, exploring mechanics and experimenting with classes. Then, the final design team takes what initial design did and makes sure everything is where it should be. It’s during this stage that most of the balancing takes place, verifying that cards aren’t too powerful or under-costed through playtesting and discussions.

Not everything makes it into the final cut, however. When asked whether or not there have been cases of ideas from the initial design team that got scrapped entirely in the later phase, Gonzalez emphasizes that “it happens all the time” in every expansion.

“When we do stuff like the art description for the art waves or talking to the effects team about what cards should we prioritize, one of the things we're always talking about is, how much confidence do we have in this card that it will survive? And sometimes cards, we like what it's doing, we like the idea of it, but it's imbalanced or it just doesn't fit in the overall scope of the year. So for those we kinda table them off and say let's do this art description and this VFX discussion when we have to, once we know if we're going to. But it's very common for cards that initial design makes to be basically torn apart because, for one reason or another, they just shouldn't fit in the expansion.”

Corpses as a new resource

While the addition of the Death Knight class made balancing a tough task due to its own mechanics, the complexity also helped to streamline the process and provide structure. Runes play their part in this, but so do Corpses, which is a secondary resource exclusive to the new class.

“It’s so appealing,” says Gonzalez, “the idea of making something that isn’t mana but you build up and spend. I think with Demon Hunter, when that class [was] in development there was a mechanic called Fury that you would build up and then spend. I wasn't on the team when it was in development, that's as far as I know—that didn't ship, obviously.”

An issue that came up during development is that, when it comes to generating and then spending the secondary resource, most cards are going do one of the two. So whenever a player draws a card that spends the resource but you never draw the card that builds it up, the effect becomes useless. Corpses are not only thematic to the Death Knight class, returning to the idea of how much a theme can influence an expansion’s mechanics, but also a great solution: All your minions are going to create a corpse upon being defeated.

“The way we can push corpse generation is by having cards like Graveyard Shift, which for 3 mana you can summon two 1 damage/1 health minions that both have Reborn,” he says. “That’s four corpses total for 3 mana, which is wild. “I love the Corpse mechanic because it's something we wanted to do for a long time, and this execution is just super simple where if a minion dies, you get one more.”

Considering all the options that Death Knight has, being on the other side of the board can be daunting. Gonzalez recognizes that there are people that enjoy taking part in matches that last for 30 minutes, but that it’s definitely not for everyone. The goal is to ensure having a variety of deck playstyles that can stand a chance regardless of their strategy. Someone who is focusing on Unholy as a primary Rune will have more corpses to spend, but those with a Blood deck will likely have a couple to spend here and there, with the attention being put into managing the board and removing minions instead.

“Corpse Explosion is maybe the exception where, there's a very good reason to try and save your corpses for that card,” he says. “It can hypothetically remove almost any board, because you just keep spending the corpses. I think that's one thing that I'm very happy with. It's the variety of ways to spend corpses, especially given how each of the runes generates them at a different pace.”

On the VFX side, the exception to the rule can prove an interesting opportunity to shift past traditions. Some cards will have a prefix saying that they don’t leave a corpse—if they were previously risen by another minion or effect, for example. Camuglia and his team asked themselves, if it doesn’t leave a corpse, shouldn’t the way that the minion dies look the same as any other minion where they crumble into pieces?

“After knocking around a couple ideas, we got a request to make a new death animation for those cards,” he says. “And I had the thought of like well, what is an unusable corpse? So I had it explode into a poof of dust instead, and kinda just crumble into ash, so there's nothing left. And I thought that was a really cool opportunity to change something about these really classic visuals that have been around in Hearthstone for a long time and put a [new] spin on it.”