The Ultimate Doom

The Ultimate Doom‘s development and release were shaped by id Software’s transition from Doom’s original distribution model to the retail market. The expansion also brought changes to the game’s levels, engine behavior, and compatibility, while Thy Flesh Consumed established a distinctly more challenging final chapter for the original Doom campaign.

For a broader look at where The Ultimate Doom fits within the series’ release history, see our Doom games in order guide.

Origins and commercial context

John Carmack described The Ultimate Doom as not being a major focus at id Software, while John Romero recalled that the decision to create it arose as part of bringing Doom into retail stores and adding an extra episode for buyers. id Software had other projects underway, and The Ultimate Doom served as the vehicle for a retail-boxed version of Doom at a point when the original shareware and registered release had already been distributed through mail order and shareware channels.

To avoid alienating the established player base who had already registered Doom, id Software released a freely available upgrade patch that brought a registered Doom version 1.9 installation up to The Ultimate Doom. Existing fans could therefore access the new episode without repurchasing the game outright.

Before the name The Ultimate Doom was settled on, the expansion was known as The Definitive Doom Special Edition. Traces of this earlier identity survive in the source code and in the DOS installer, where the titlebar reads DOOM: Special Edition and the suggested default installation directory is DOOM_SE. An early version of the executable included in the 2015 Doom source data release displays the startup title DOOM System Startup 1.9 Special Edition in black characters on a cyan background, contrasting with the final release’s The Ultimate DOOM Startup v1.9 in dark gray on a light gray background.

The design team

The creative lead on the expansion’s new content was John Romero, working alongside American McGee and Shawn Green. Romero recruited two designers who had made names for themselves in the rapidly growing Doom fan community.

The first recruit was John Anderson, who went by the handle Dr. Sleep. Anderson would later collaborate with Romero again on Daikatana. The second was Tim Willits, who took a very different trajectory: he went on to become id Software’s lead designer. A small number of new graphic assets were produced by the team’s artists to support the new episode’s visual identity.

Romero himself designed two of the nine Episode 4 levels: E4M2: Perfect Hatred, and E4M6: Against Thee Wickedly.

Romero also took the opportunity to revise the first level of his original first episode, Knee-Deep in the Dead. He added openings into the central courtyard to improve movement between players during deathmatch games.

Thy Flesh Consumed

The fourth episode, Thy Flesh Consumed, consists of nine maps (E4M1 through E4M9) and is narratively positioned as occurring between the events of the original Doom and those of Doom II. The closing text of Episode 3 had placed the protagonist on Earth after stepping through Hell’s hidden doorway; the ending of the new episode makes clear that the spiderdemon had already dispatched its legions to rampage through Earth’s cities, setting the stage for Doom II’s urban catastrophe.

The episode title and every level name except E4M9: Fear were taken from phrases in the King James Version of the Bible. The list of phrases was compiled by Kevin Cloud, and John Romero assigned the names to the individual levels.

The episode’s maps made use of engine features that had been present in the executable but were largely unused in the original three episodes. Sector type 17, key-requiring switches, and linedef actions such as blazing doors — all carried over from Doom II’s feature set embedded in the shared engine — found application in the new levels.

The maps are generally considered much harder than those of the first three episodes and Doom II. The full map roster across all four episodes is as follows:

• Episode 1 — Knee-Deep in the Dead: E1M1: Hangar, E1M2: Nuclear Plant, E1M3: Toxin Refinery, E1M4: Command Control, E1M5: Phobos Lab, E1M6: Central Processing, E1M7: Computer Station, E1M8: Phobos Anomaly, E1M9: Military Base
• Episode 2 — The Shores of Hell: E2M1: Deimos Anomaly, E2M2: Containment Area, E2M3: Refinery, E2M4: Deimos Lab, E2M5: Command Center, E2M6: Halls of the Damned, E2M7: Spawning Vats, E2M8: Tower of Babel, E2M9: Fortress of Mystery
• Episode 3 — Inferno: E3M1: Hell Keep, E3M2: Slough of Despair, E3M3: Pandemonium, E3M4: House of Pain, E3M5: Unholy Cathedral, E3M6: Mt. Erebus, E3M7: Limbo, E3M8: Dis, E3M9: Warrens
• Episode 4 — Thy Flesh Consumed: E4M1: Hell Beneath, E4M2: Perfect Hatred, E4M3: Sever the Wicked, E4M4: Unruly Evil, E4M5: They Will Repent, E4M6: Against Thee Wickedly, E4M7: And Hell Followed, E4M8: Unto the Cruel, E4M9: Fear

Unlike the first three episodes, Thy Flesh Consumed does not use a progression map on its intermission screen. Instead, it uses a grayscale version of Doom II’s intermission background.

PC Zone’s August 1995 issue took aim at the price of the release, giving it the tongue-in-cheek verdict “Thy Cash Consumed” for readers who already owned Doom. The review criticized the repackaging as a way of extracting more money from an already successful game, while newcomers received the separate verdict “Thy Spare Time Consumed.”

Engine changes and compatibility notes

The underlying executable received targeted modifications rather than a comprehensive overhaul. Programmers added the text strings necessary for the new episode, inserted a fourth-episode demo into the rotating demo sequence, and adjusted boss death triggers to handle the new boss encounters in Episode 4’s sixth and final maps. That last adjustment introduced a compatibility problem with a few PWADs that had been built around the earlier behavior.

A long-standing bug was also corrected: in prior releases, lost souls did not bounce off floors as the designers had intended. Lost souls still do not bounce off ceilings, even in versions where the floor-bouncing bug is fixed. The fix, while welcome, caused previously recorded demos featuring those monsters to desync during playback.

Despite these changes, the executable still internally identifies itself as version 1.9 and functions like Doom 1.9 in most respects. It can load the 1.9 versions of Doom and Doom II, though with a wrinkle: the executable still expects a fourth demo in the sequence, so the program terminates immediately after the third demo when running those older IWADs. Running the non-Ultimate 1.9 Doom IWAD additionally causes a crash at the episode-selection screen because the engine expects the M_EPI4 lump and cannot find it.

Modern re-releases

The Ultimate Doom has been included in several modern re-releases of the classic game. The 2019 Doom Classic Unity port, released on July 26, 2019, presented the game through the Unity-based modern port, with cheats accessed through the Options menu.

On August 8, 2024, Doom + Doom II introduced a new version built on Nightdive Studios’ KEX Engine, replacing the earlier Unity-based release on most storefronts. The Unity port remains available on Android and iOS, while the Steam and GOG versions of Doom + Doom II also include the Unity port as a bonus. The package includes The Ultimate Doom alongside Doom II and additional classic and modern content. The DOOM.WAD included at launch is 12,733,492 bytes.

Speedrunning

The Ultimate Doom has an active speedrunning community. The Doom Speed Demo Archive tracks records across all four episodes, as well as full-game runs. The current full-game UV Max record is 1:16:53, achieved by kuckkuck on April 22, 2025, using DSDA-Doom. GuyNamedErick’s 2:29:50 run, recorded on February 11, 2018, is currently the second-fastest full-game UV Max run and requires playback in CNDoom.

For a broader chronological view of The Ultimate Doom alongside other major releases, source-code milestones, and developments in the Doom community, see our Doom timeline.

Community legacy

The Doom Wiki counts E4M2: Perfect Hatred and E4M1: Hell Beneath among the most difficult maps in the episode and the Doom series.

The episode has also served as the direct inspiration for major community projects. Ultimate Doom the Way id Did tasked community designers with creating a new Episode 4 faithful to the aesthetic and design philosophy of the original team. The Cacoward-winning 2023 megawad Ultimate Doom In Name Only reimagined all 36 maps of The Ultimate Doom with entirely fresh geometry and layouts, retaining only the original level names as conceptual anchors. Both projects reflect the enduring centrality of this release to the classic Doom community’s creative tradition.