FIX: Lex Imperialis DLC Failed to Start in Warhammer 40K

If the Lex Imperialis DLC fails to start in Warhammer 40,000: Rogue Trader, you might see the error message “Failed to initialize DLC: LexImperialis”, along with blank tooltips, missing item descriptions, or no sign of the new DLC content.

It is usually caused by leftover mod files (often from ToyBox), a corrupted install, or the DLC not being enabled in Steam. Find below every proven fix to get your game back on track without losing progress.

How to fix the Lex Imperialis DLC failed to start error

1. Delete Leftover ToyBox Files 🚫

1. Close the game completely
2. Press Windows + R on your keyboard. In the box that pops up, type this and hit Enter: %LOCALAPPDATA%\Owlcat Games\Warhammer 40000 Rogue Trader\UnityModManager\0ToyBox0
3. Delete that folder
4. Now go here and delete the ZIP file if you see it: Steam\steamapps\workshop\content\2186680\3107755014\0ToyBox0.zip
5. Start the game again
6. Press the ESC key, click Mods, and make sure Lex Imperialis is turned on
7. Travel to a different star system. This can help trigger the first DLC quest

Even if you don’t use the ToyBox mod anymore, some files might still be causing problems.

2. Unsubscribe from ToyBox in Steam 🔌

1. Go to the Steam Workshop page for the game
2. Find ToyBox in your list of subscribed items and unsubscribe
3. Then, go to this folder: Steam\steamapps\workshop\content\2186680\3107755014\
4. Delete that folder too

3. Check Game Files in Steam 🤖

1. Open Steam
2. Right-click Warhammer 40,000 Rogue Trader
3. Select Properties
4. Click Installed Files on the left
5. Now click Verify integrity of game files

This same process has fixed issues in other games too, like Dawn of War 3, where broken installs caused random crashes.

4. Make Sure the DLC Is Turned On 🔛

In Steam:

1. Right-click the game
2. Click Properties
3. Go to the DLC tab
4. Make sure Lex Imperialis is checked

In the game:

1. Press ESC
2. Go to Mods
3. Make sure Lex Imperialis is turned on

💡 Note: Once the DLC is turned on in your save file, you can’t turn it off again.

5. Start a New Game with the DLC Enabled 🕹️

1. Start a new game
2. Make sure Lex Imperialis is turned on before you start
3. Travel between star systems to trigger the first DLC quest

If you added the DLC in the middle of a campaign, it might not load correctly. Try starting a new game and see if it’s working.

6. Reinstall the DLC ♻️

1. In Steam, go to the game’s DLC tab
2. Uncheck Lex Imperialis to uninstall it
3. Close Steam completely
4. Go to this folder and delete it: Steam\steamapps\common\Warhammer 40000 Rogue Trader\DLC\LexImperialis
5. Open Steam again
6. Go back to the DLC tab and check Lex Imperialis to download it again

Having the right system specs helps too. Some players ran into DLC loading issues with older setups. If you’re unsure, check out the minimum requirements for Dawn of War 3 to get a general idea.

7. Turn Off Other Mods ❌

1. Press ESC in-game
2. Go to Mods
3. Turn off all mods except Lex Imperialis
4. Restart the game

8. Clear Mod Cache and Reinstall UnityModManager 🧹

1. Press Windows + R, then paste this and press Enter: %LOCALAPPDATA%\Owlcat Games\Warhammer 40000 Rogue Trader\UnityModManager\
2. Delete everything inside that folder
3. Download and reinstall the latest version of UnityModManager from its GitHub page

Conclusion ✅

Lex Imperialis brings a whole new chapter to Rogue Trader with fresh characters, gear, and story choices that add depth to the game. Getting past this DLC error means unlocking all that extra content and experiencing the full Warhammer 40,000 world as intended.

Remember, taking the time to fix these issues ensures your adventure stays smooth and engaging. Just in case you’re having overheating GPU issues while playing the Lex Imperialis expansion for Warhammer 40000: Rogue Trader, don’t forget to check out this guide.

FAQ ❓