JOHN ROMERO HAS made dozens of games. Counting titles written but never published during his earliest forays into programming, he’s made hundreds.

To call him prolific would be a gross understatement. While Romero’s most popular titles originated on the PC, he is the personification of platform agnosticism. If a piece of hardware is even remotely capable of running game software, he has likely developed for it.

But of all the games he’s designed, Doom may mean the most to him. “The design of everything worked so perfectly, the way I wanted it,” he told me several years ago. “It was all about friction, acceleration, and speed. I tweaked all those values until it felt perfect to me. So when I play the game, it's exactly what I want to be playing. To me it's optimal.”

Doom is widely considered to be id Software’s opus. That makes Sigil, the game’s unofficial fifth episode, all the more special. Due for release as a free download in the spring of 2019, Sigil features nine levels, all designed top to bottom by Romero.

Icon of Sin charts the steps Romero walked to return to designing maps for Doom after a quarter century away, and features interviews with some of the individuals who teamed with him to give Sigil an extra shine.

Icon of Sin was written based on research and interviews conducted over Skype and email. The views expressed therein are those of the individuals who provided them and do not reflect the opinions of the author, Shacknews, or its parent, affiliate, or subsidiary companies.

SPOILER WARNING: Icon of Sin goes into detail on the making of Sigil, John Romero’s expansion for the original Doom. As such, there are light spoilers on specifics such as elements of level design and boss fights.