Last week, to much popular acclaim, Blizzard announced the development of Diablo IV, the latest sequel in its long-running action RPG franchise.

As more details on the game have emerged during BlizzCon this weekend it's become clear that the veteran developer is making some serious changes to the franchise, with a new engine, a new aesthetic, and new possibilities for the popular dungeon crawling series.

During the show, lead systems designer David Kim and lead lighting artist Sean Murphy were able to share some insight about what it's like working on Diablo IV and explain some of the key ideas driving the game's development.

Hellishly good systems

Both Kim and Murphy began discussions of their respective work by discussing the core game pillars touted onstage during the game's debut. "Return to Darkness," "Embrace the Legacy," and "The World of Diablo."

For Kim (who previously worked as a designer on Starcraft II), "Embrace the Legacy" proved to be where a lot of his design focus would wind up. "At the core of it, we're trying to make a Diablo game first," said Kim. "On top of that, we're trying to take the great parts of each of the previous Diablos and bring it to Diablo IV, and bring in elements from other types of games as well."

Drawing on older Diablo games, Kim explained that some player abilities have been directly inspired by fan-favorites such as the sorceress class' frozen orb ability. But as a lead system designer, Kim says the next step is to imagine ways players can upgrade and tweak those abilities to fit a specific playstyle.

For the frozen orb, Kim cites a particular legendary item that lets players shoot down frozen orbs mid-air, blowing them up early, creating essentially a brand new skill. "So we want to do more of that," said Kim. "We want to increase the number of playstyle options and customizations across the board throughout leveling as well as in the endgame."

That's why Kim says, they've implemented a new skill point system that unlocks and ranks up player skills and revamped the game's talent trees, all with the goal of encouraging players to take more control over their playstyle and abilities.

But while updating granular abilities is sure to attract veteran Diablo players, Kim's also had his eye on how Blizzard has to adapt with the changing world of online games. Seasons for instance, are a continued feature from Diablo III, that allow players to make progress in a specific window of time in different game systems, earn unique items, and gain prestige in Diablo's leaderboards.

In Diablo IV, Kim in particular discussed the distribution of legendary items, and creating season-specific legendary items that can help create unique play experiences for longtime players. "We want to make sure we're including brand new legendary items in seasons, we want to also make sure that we have subset of legendaries that are more powerful from season to season, and the subset is changing."

But when it comes to how progression works in seasons, Kim says some of those decisions are still up in the air. Kim discusses one possible change that comes from a lot of time spent playing through World of Warcraft's later endgame progression systems.

He pointed out a balance change they made in the Artifact and Azerite weapon systems that allowed players to cap out their total power, instead of endlessly grinding for loot. "So that makes me thing, 'okay, is the endless grind that we had in [Diablo III's] paragon system, is that the right call? Or is there something cool about having a cap to it too?

According to Kim, he brought that idea back to a Diablo design meeting, that helped the team challenge some of their assumptions about how Diablo handles progression. "We never looked at it that way, we just assumed endless grind is the best."

"But that capped feeling gives players a sense of 'okay, I did it, I'm super powerful now, let me use all the cool things I've learned. If you have an endless system it's "I'm always chasing after something that I can never achieve.'"

Kim says Blizzard hasn't quite figured out how it would want to implement a system like that, but it's a clear example of ways the developer is trying to keep Diablo feeling fresh.

Lastly, it's worth noting that in a world of growing online games, Kim explained that Blizzard is looking to keep all player experience equally valuable, and to not communicate a sense of "missing out" that some online games do if players can't log in on a particular day.

"We're going to stick with what is Diablo, which we think is 'you can play as much or as little as possible on a given day, and it's not really affecting you in a negative way,'" Kim said. "If I play ten hours [in a day] versus if I play ten hours over the course of two weeks it's a very similar amount of hours I'll be getting. So you can control how you're playing the game."

Looks that could kill

During a discussion of Diablo IV's art style, Murphy revealed a fourth "internal" pillar he and his coworkers have been adhering to: "Old Master's Influence."

"Our goal is sort of--we want to make a medieval masterpiece, is what we call it. It's a very classical, painterly approach with naturalistic colors. We look at Rembrandt, we look at Remington's nocturnals. There are natural color pallettes and the tonalists like George Inness, which are very grayscale."

One clear example from the game's cinematic trailer is the reveal of Lilith--a demon draped in a blood veil whose striking reveal can be seen up above.

Murphy says this direction was chosen in a further attempt to "embrace the legacy," that other aforementioned pillar. "A lot of us really gravitate toward the Diablo II aesthetic, and the more grounded and visceral experience," he explained.

"It also partners up really well with what we're trying to do with [building] the overworld. We're trying to make Sanctuary (the world of Diablo) real."

"You'll see across the Diablos from 1 to 2 to 3, there was like "hey you're in Tristram" in Diablo, Diablo II had a couple more locations, and Diablo III a couple more locations. But they're still sort of scattered out, and here we're going to give a continuous vibe of pretty large regions to travel across."

Though Diablo and Warcraft are both magic-laden fantasy RPG franchises, Murphy says Diablo's strength is its ability to be a darker, more mature-themed game at Blizzard. Though "mature" is still something of a challenging keyword for the company.

"We don't like to gratuitously do things and we don't like to do things whether we're using blood or flayed people...we use that for effect to tell a [visual] story."

This posed a question though, of how Blizzard could prevent that mature tone from just fading into the background when players are replaying familiar dungeons or areas. "A lot of what you'll see in the environments comes with the art, in these things we call culture kits," said Murphy. These appear to be a toolkit of assets that can be arranged by the visual art team to create different background stories that fill out a space.

He referred to two different dungeons in the BlizzCon demo both fueled by the same culture kit: one filled with the victims of a goatman invasion, and the other a barnacled set of caverns filled with fearsome sea creatures. "They're actually the exact same tiles but they look completely different."

The goal it would seem, is to use those ghoulish elements every time a player passes through the zone to give a sense of character to the place they're exploring, with different levels of maturity that can reveal themselves depending on what rooms spawn in the dungeon.

Lessons from building a new game

Both Kim and Murphy had helpful thoughts for other developers based on their Diablo IV experience. For Kim, the biggest lesson he's learned so far was part of his transition from the Starcraft II team to the Diablo IV team. " I had my worries of, what it's gonna be like designing a completely different type of game," he said.

"But kind of the interesting lesson learned for me is a lot of the design philosophies transfer over pretty well. And it's a lot of how much I've kind of dug deep into RPG games as a player. I noticed what I was doing was as I'm playing, I'm analyzing what I'd do, all the pros and cons, for a very long time, because I love RPG games."

"So I think if anyone's thinking about a transition because they love this genre but they haven't worked on it before, I'd strongly encourage if your design fundamentals are strong, and if you've been analyzing all these different types of games you love to play, it should be a much smoother jump then you expect."

For Murphy, his lessons have to do with the transition from one engine to another. "We're making a new game, we have a new engine, we have a new renderer..that doesn't mean the best thing you can do is go create a whole bunch of problems you have to solve that might not move the game forward," he said.

"Starting sort of small and building as you need to pull more features online, whether it's dynamic coastlines or weather systems or deformable terrain or snow, don't just look at it like a shopping list, you know? "Because you're just going to make a big headache for yourself for a feature that might not be useful down the road."

Both team leads above all else seemed excited to finally share Diablo IV with the world, and emerge from a self-imposed shroud of darkness that's kept them from sharing exactly what they're working on up to this point.