AI Darth Vader was a huge hit in Fortnite, and now Epic plans to let creators make AI-powered NPCs for their own in-game experiences. But a senior Epic exec says that creators should expect a “learning curve” when using them — something Epic had to figure out on its own.

The AI Vader that Epic made lets users talk to the character using their voice and hear an AI-generated version of James Earl Jones’s Vader voice talk back. It was the “culmination of a very intense effort for a character everybody understands,” Saxs Persson, Epic’s EVP of the Fortnite ecosystem, tells The Verge.

But Epic couldn’t just set an AI chatbot loose — “a lot” went into defining how Vader reacted and dialing in the voice. The work was worth it, though; in-game, Vader’s voice sounds just like the movies, and when he’s on your team, he’s a menacing, aggressive force. Persson says that Vader was ultimately “integrated into gameplay in a way that every player could understand” and he hopes creators are able to make similar things.

Vader’s rollout wasn’t perfect; a popular streamer, Loserfruit, was able to get Vader to swear, which Epic fixed shortly after it happened. Persson says that it was a “learning experience” and that the team has built multiple layers of how it does its safety checks.

Epic also tries to build systems to prevent those kinds of things and be able to react fast. “We do our best job on day one,” Persson says. “But more importantly, we’re ready to surround the problem and actually have fixes in place as fast as we can.” Creators making AI NPCs for Fortnite will have access to the same safety tools that Epic did for Vader.

At Unreal Fest on June 3rd, the company showed a live demo of an AI NPC called Mr. Buttons, whose only purpose was, using its voice, to try and convince the player to push a giant red button. It was a simple, effective, and funny demo that showed what’s possible. The goal was to create a scenario where “the responses are literally endless” so that “everybody has a different experience,” Persson says.

Persson wouldn’t say if or when Epic plans to bring more AI NPCs to Fortnite. He says that Epic didn’t give its designer some kind of “AI objective” when making Vader. “Our objective is fun,” CEO Tim Sweeney says. “AI is just another tool they have now,” Persson adds. It sounds like AI characters could show up in Epic and Disney’s “persistent universe” that’s in the works, too: “I would imagine that AI plays a role,” Persson says, noting that it would help with immersion.

Persson wouldn’t share a timeline for when the universe, which was announced last year, might be available. But Epic is going to let creators make their own Star Wars-themed experiences, so perhaps somebody will create another take on an AI Darth Vader.