Diablo, the titular Lord of Terror, was largely absent from Diablo 4's base game and post-launch expansions because the character himself is "very demanding," according to developers. Instead of appearing as downloadable content, Diablo will be the central antagonist in the upcoming Diablo 5, a sequel revealed at BlizzCon.
Senior production director Tiffany Watt and senior art director John Mueller explained that the original vision for Diablo 4 centered on Lilith. Tacking Diablo onto that narrative as an expansion would have been challenging, Mueller stated. "We do have a luxury [at] Blizzard in that Blizzard supports us in what we want to build, and I think there was no container on our vision or anything," Mueller said. "It was like, just build the greatest Diablo game that you have a vision for. That could be an expansion, that could be a sequel, it could be anything you want."
The developers felt that when Diablo is the focus, the story needs to be ambitious and cannot be contained within a smaller scope. This ambition is what led to the decision to pursue Diablo 5 as a full sequel, allowing the team to innovate and deliver a more impactful narrative experience.
"You can’t tell a small story, and then when you decide that you’re making a sequel, and all of a sudden you have to be bold, you have to be ambitious, you have to innovate, and it kind of unlocked a lot of things for us," Mueller elaborated. He noted a desire to move toward more personal, character-driven narratives, citing the upcoming Lord of Hatred expansion for Diablo 4 which features player relationships with Lilith and Mephisto. However, the team aims for this level of personal investment to be a core component of an entire game, a goal more achievable in a sequel.
"You should feel like the stories matter, the characters matter, this should feel like the cast of your favorite show, and that’s what we’re trying to achieve," Mueller said. "So those are the things that doing a sequel really opens up for us, because we have the talent, we have the tech, we have the skills, but the framework of the game has to change."
Diablo will appear as a seasonal boss in Diablo 4's upcoming Season of Hell's Legacy, but his full potential as a protagonist will be explored in Diablo 5, where he has conquered the world, leaving players to fight within a literal hellscape.