Final Doom is a compilation of two standalone Doom II modifications, TNT: Evilution and The Plutonia Experiment, which include full sets of new levels (both of them use the same level structure as Doom II with 30 regular levels and 2 secret levels), new graphics and textures, and new text interlude screens in addition to most of the resources from Doom II and some from Doom. TNT: Evilution contains a new soundtrack, while The Plutonia Experiment uses music from Doom and Doom II: Hell on Earth. It was published in June 1996 by id Software under the initiative of John Romero and developed by members of the fan community belonging to TeamTNT.
TNT: Evilution was developed independently by TeamTNT, and was purchased by id Software when it was practically complete. The Plutonia Experiment, on the other hand, was created specifically for Final Doom after its authors showed some of the id Software developers an incomplete set of levels. Its two authors, while part of TeamTNT and also contributors to TNT: Evilution, produced The Plutonia Experiment independently.
Each of the two standalone IWADs is presented as a sequel to Doom II, referencing events from the original game in their background stories, particularly the invasion of Earth, but without referencing each other in any way.
Since the Final Doom IWADs each contain most of the resources from Doom II, and replace the rest, they can be used along with add-ons made for Doom II, notwithstanding some possible visual inconsistencies of minor importance.
It is not clear who made the modifications to the engine. Final Doom uses the sources from The Ultimate Doom, being identical to the engine from the expansion of Doom in most respects (and is likewise marked as v1.9 regardless of differences). It is even capable of running Thy Flesh Consumed if used with the corresponding IWAD, but also detects the new Final Doom IWADs and adds the necessary text strings for the intermission screens and level names when needed (and without losing the data needed to run Doom II). If a user places various IWADs in a single directory the engine selects the new IWADs before Doom II or Doom, and The Plutonia Experiment before TNT: Evilution.
Since it is derived from the source used for The Ultimate Doom, it may also display incompatible lost soul behavior when playing demos recorded with Doom version 1.9. There is, however, one additional minor difference that may also affect compatibility, a bug in the teleportation behavior where the altitude of a teleporting thing is not checked.
- When using Final Doom's engine, setting joyb_speed to 31 in the configuration file doesn't make the player always run as in version 1.9, though the value of 29 works in all versions.