Gamers are gobbling up those souls.

Publisher Bandai Namco’s American branch revealed today that the punishing action game Dark Souls III has become its fastest-selling game. It also had the best first day sales in Bandai Namco Entertainment America’s history. The company did not provide specific sales numbers (we have asked and will update this story if we get exact figures). It’s a clear sign that the series is doing better than ever. Dark Souls III launched on April 12 for PlayStation 4, Xbox One, and PC.

The Souls series is important to Bandai Namco because of its appeal to audiences outside of Japan. Many of the company’s other gaming series are based on anime like Dragon Ball Z or Naruto. These games still have an audience in the U.S., but it’s niche compared to the appeal the Souls series has.

The series actually started in 2009 with Demon’s Souls for the PlayStation 3. While it was a well-received game, few would have guessed it would spawn one of the most popular franchises in gaming today. In a lot of ways, the series is the opposite of modern blockbuster experiences. It’s slow-paced and brutally difficult.

Still, its methodical, rewarding gampeplay has attracted millions of fans. Before the launch of Dark Souls III, the series has sold around 8.5 million copies (and that doesn’t include the offshoot Bloodborne or the original Demons Souls). With this strong start, it’s likely Dark Souls III will end up as the best-selling entry in the series.

Updated at 9:02: This story originally noted that Demon’s Souls sold 1.7 million numbers, but those figures have come into question as being from an unreliable source. We removed that number and instead only reported the sales for the Dark Souls series.