John Romero will release a new Doom episode, Sigil II, on December 10 for its 30th birthday

One of the founders of id Software, John Romero, is getting ready to release a new episode for perhaps its most influential game, Doom. The new episode, Sigil II, will be released on December 10, which happens to be the 30th anniversary of Doom's release in 1993.

Romero previously created and released the first Sigil episode for Doom back in 1993 for free as an unofficial fifth episode of the main game. It was later released by id Software's current owners, Bethesda Softworks, as a free mod for its Doom ports for consoles and mobile devices.

Sigil II will, naturally, be considered as Doom's unofficial sixth episode when it launches. It will have nine levels along with two Deathmatch-only levels. While the new episode will be released for free, Romero is selling a digital edition that will also contain the level pack's two digital soundtracks from Thorr and James Paddock.

Romero is also selling a physical edition installed in a custom USB Flash drive shaped like a shotgun shell along with some other digital and physical extras. Two other physical editions of the game have already sold out.

In addition to the release of Sigil II, Romero will be joining in an online chat on December 10 on his Twitch channel with fellow id Software founder John Carmack to discuss the release of Doom 30 years ago. The chat will be held at 8 pm GMT (3 pm Eastern time).

Romero's current game development company, Romero Games, is also working on a major upcoming Unreal Engine-based first-person shooter project but details have yet to be announced.