DOOM 3: Complete Guide & Walkthrough Outline

A player's guide to the Steam DOOM 3 package: which version to play, weapons and enemies, a level-by-level outline, boss strategies, Resurrection of Evil and The Lost Mission, plus fixes and mods for modern PCs.

Researched September 2026 — current as of the combined Steam listing (original 2004 DOOM 3 + Resurrection of Evil, and DOOM 3: BFG Edition; last update January 2023 added DPI awareness to BFG Edition). Live games change; check the linked sources if something differs.

What You Get on Steam

Since id Software consolidated its Steam listings in August 2022, buying DOOM 3 gives you both:

Which to play? First-timers usually prefer the BFG Edition for the armor-mounted flashlight and controller support. Purists pick the original (optionally with a source port, see below) for the intended darkness and free saving. The BFG Edition's flashlight runs on a recharging battery, so there's still some tension.

Quick Start

1. Read PDAs. Every PDA you pick up gives security clearance and emails/audio logs that often contain storage locker codes with ammo and armor.
2. Always check corners and behind you. Doom 3 loves monster closets and imps teleporting in behind the player.
3. The Shotgun is your best friend for most of the game; point-blank blasts kill imps and zombies in one or two shots.
4. Save the BFG and Rocket Launcher ammo for boss fights and big hordes.
5. Grab health stations (wall-mounted) when you're below half; many are near arenas.
6. Use the Chainsaw on Pinky demons and zombies to conserve ammo.
7. Stamina matters in the original version: sprinting drains it, and you'll need it to escape bad fights.
8. Nightmare difficulty unlocks after you beat the game once. Your health drains to 25 and the Soul Cube is available from the start.
9. In the original version, quicksave often (F5 quicksave / F9 quickload). BFG Edition uses checkpoints plus manual saves.

Controls (default PC)

Remap freely in the Options menu.

Weapons

Resurrection of Evil adds the Double-Barreled Shotgun, the Grabber (a gravity gun that catches and throws objects and projectiles, including imp fireballs) and the Artifact.

Enemies to Know

Level-by-Level Outline

The campaign is linear. Main areas in order:

1. Mars City (arrival, introduction, meet Sergeant Kelly)
2. Mars City Underground (the invasion begins)
3. Mars City (return, now overrun)
4. Administration
5. Alpha Labs Sectors 1 to 4
6. EnPro Plant
7. Communications Transfer and Communications
8. Monorail Skybridge, Recycling Sector 2, Monorail
9. Delta Labs Levels 1, 2A, 2B, 3 and 4
10. Hell
11. Delta Complex, CPU Complex, Central Processing
12. Site 3
13. Caverns Areas 1 and 2
14. Primary Excavation (finale)

Section tips

• Mars City to Administration: ammo is tight. Use the pistol and flashlight carefully; search offices for PDAs and lockers.
• Alpha Labs: a science-lab stretch with more Imps, Maggots and the first bigger demons. Hunt for PDAs here; several lockers pay off later.
• The Vagary (first boss): a large spider-like demon that throws objects at you telekinetically. Keep moving laterally, dodge the thrown objects and use the Shotgun/Machine Gun between throws. Beating it unlocks the "Sticky Situation" achievement in the BFG Edition.
• EnPro and Communications: more open arenas; Hell Knights appear. Save Rocket Launcher ammo for them.
• Monorail and Recycling: tight corridors and ambushes; keep grenades for rooms.
• Delta Labs: teleportation research. Expect heavy monster spawns; this is where the Plasma Gun and bigger threats show up.
• Hell: a dark, dreamlike level ending with the Guardian of Hell, a huge blind demon that relies on small flying Seekers to find you. The fight revolves around those Seekers: deal with them, keep moving so the Guardian's charges miss, and punish the openings. Defeating it earns the Soul Cube.
• After Hell: Sergeant Kelly's true nature is revealed, and later you fight Sabaoth, the cyborg he has become, armed with a BFG. Its BFG orbs are slow: sidestep them, use cover, and answer with rockets or your own BFG.
• Primary Excavation: the Cyberdemon. Other weapons only stagger it; you must charge the Soul Cube by killing the small enemies that keep spawning, then fire it at the Cyberdemon (it takes several Soul Cube hits).

Resurrection of Evil (Expansion)

Set two years after the original. A new marine recovers the Artifact from the ancient Martian ruins.

• Artifact powers are unlocked by beating the three Hunters: Hell Time (slow motion), Berserk (huge melee damage) and Invulnerability. The Artifact is charged by souls from dead enemies.
• Grabber: catch imp fireballs and hurl them back, or throw barrels. It's great for conserving ammo.
• Double-Barreled Shotgun: high burst damage; the go-to close-range weapon.
• New enemies include the Vulgar, Bruiser and Forgotten One. The final boss is Maledict.
• Tip: Hell Time + Double-Barreled Shotgun trivializes many big fights; save Artifact charges for Hunters and ambush rooms.

The Lost Mission (BFG Edition Only)

A short additional campaign following a survivor from the Bravo Team during the original events. It reuses DOOM 3 assets with new layouts and fights, and is tuned for players who've finished the main game. Treat it as a greatest-hits challenge: ammo is manageable, fights are dense.

Difficulty

Collectibles and Achievements (BFG Edition)

The BFG Edition's Steam achievements cover all three campaigns plus the embedded DOOM and DOOM II. The ones worth planning for:

• PDAs, lockers and video logs are all missable-feeling but can be done in one careful run: read every PDA for codes and check every office and body.
• Difficulty achievements are separate per difficulty, so plan a Nightmare run on its own.
• Resurrection of Evil (one achievement per Hunter, plus Maledict) and The Lost Mission have their own sets.

Common Mistakes to Avoid

• Ignoring PDAs and missing locker codes (which often hold armor and ammo you need).
• Walking backward into unexplored rooms. Monster closets open on triggers; move forward carefully and turn around after grabbing items.
• Firing rockets at point-blank range. Splash damage hurts you too.
• Using the BFG on trash mobs before Sabaoth and the Cyberdemon.
• Fighting in open rooms without backing up into a corridor. Pull enemies into chokepoints.
• Forgetting the Soul Cube is the only way to kill the Cyberdemon.

Advanced Tips

• Shotgun jump-strafe: close the gap and fire; the shotgun's spread is tight enough at point-blank to one-shot imps.
• Grenade bounces clear rooms before you step in.
• Health station farming: stations have limited charge, but you can top off before triggering an obvious arena.
• Original version stamina: walk most of the time and save sprint for escape.
• Z-Sec shield soldiers: chainsaw or flank; grenades bypass shields.
• Console (PC): to use the console add +set com_allowConsole 1 to launch options, then press the tilde key. Avoid cheats on a save you care about achievements on.

Modern PC Fixes and Mods

• dhewm3 is an open-source port of the original DOOM 3 (and Resurrection of Evil) for modern Windows, Linux and macOS. It uses the game data from your Steam copy of the original version (patched to 1.3.1) and does not support the BFG Edition.
• RBDOOM-3-BFG is a modernized source port of the BFG Edition engine with improved rendering and features.
• Duct Tape mod (original) attaches the flashlight to your weapons, mimicking the BFG change without leaving the original version.
• Perfected Doom 3 and Sikkmod are popular visual/gameplay overhauls for the original.
• Frame rate: the original engine was tied to 60 Hz logic; source ports handle modern refresh rates better than tweaking configs.
• High DPI: the January 2023 update added DPI awareness to the BFG Edition, which fixes blurry scaling on high-DPI displays.

FAQ

Should I play the original or BFG Edition? BFG for comfort and extras (Lost Mission, flashlight on armor, controller support). Original for the authentic dark experience and quicksave-anywhere, ideally through dhewm3.

How do I beat the Cyberdemon? Kill the small enemies it spawns to charge the Soul Cube, then fire the Soul Cube at it. Repeat until it dies. Other weapons can't finish it.

Where do I get the Soul Cube? From defeating the Guardian of Hell in the Hell level.

Do I need to play Resurrection of Evil after the main game? It's a sequel and assumes you've finished DOOM 3. You start over with a fresh arsenal, but the fights are tuned for experienced players.

Why can't I open the console? Add +set com_allowConsole 1 to the Steam launch options.

Is the BFG Edition missing anything from the original? The lighting and some textures were adjusted and saves are checkpoint-based; mods for the original don't work in BFG. Both versions are included on Steam, so you can play whichever you prefer.

Sources

• DOOM 3 on Steam (store listing and news)
• Steam news: id Software store listing consolidation (Aug 2022) and BFG DPI update (Jan 2023)
• DOOM 3 — Wikipedia
• DOOM 3: BFG Edition achievements (Steam)
• dhewm3 source port (GitHub)
• RBDOOM-3-BFG (GitHub)