After investigating this particular issue thoroughly, it turns out that there are several different potential culprits that might be triggering this particular issue. Here’s a list of scenarios that might directly or indirectly cause the ‘Fatal Error’ when launching Dungeon Defenders 2: Now that you know very potential culprits that might be responsible for this issue, here’s a list of methods that other affected users have used successfully to fix this particular issue.
Method 1: Deleting the Unreal Development Kit Files
As it turns out, the most common instance that might be responsible for the ‘fatal error’ message is a collection of corrupted files belonging to the UDK (Unreal Development Kit) library. Several affected users have confirmed that the issue was finally fixed after they manually navigated to the location where these files are stored and deleted all of them from the Config folder. Note: Keep in mind that these files are automatically generated and have regenerative capabilities. This means that even if you delete them and they’re not the source of the issue, the game installation is perfectly capable of regenerating them from scratch. In this particular case, the ‘Fatal Error‘ is known to occur at the launch of Dungeon Defenders 2 due to the way these UDK files are being distributed within the Steam installation. One solution around this issue is to navigate to the directory where the UDK files are stored and deleting them manually in order to eliminate the issue: If you already followed the instructions above to delete the UDK files and you’re still seeing the same fatal error when you attempt to open Dungeon Defenders 2, move down to the next potential fix below.
Method 2: Whitelisting Dungeon Defenders 2 + Steam in AV Settings
In case you previously established that the ‘fatal error’ issue is not being caused by some type of corruption associated with the UDK files, the next thing you should investigate is your antivirus. Keep in mind that there are a lot of user reports saying that they’ve discovered that the security app was actually responsible for this problem after it ended up preventing the game from using every required dependency due to a false positive- This issue is confirmed to occur with both 3rd party security suites (firewall + antivirus) and the integrated security solution (Windows Defender + Windows Firewall). If this scenario is applicable, the fix is simple – You need to establish a whitelisting rule in your AV / Firewall that will whitelist both the main executable and the Steam launcher that you use to launch the game. Note: In case you’re using a 3rd party security suite, the exact instructions for establishing a whitelisting rule will be different from developer to developer. If you can get this done by yourself, look online for specific instructions. On the other hand, if you’re using Windows Defender + Windows Firewall (the native security options on Windows 10), you can follow the step-by-step instructions below to establish an exception rule for the main Dungeon Defenders 2 game executable and the Steam launcher: In case you’re still seeing the same ‘Fatal Error‘ even after whitelisting the main game executable + Steam, move down to the next potential fix below.
Method 3: Disabling or Uninstalling the Overprotective AV Suite (if applicable)
If you followed the instructions above to successfully whitelist the main game’s executable + Steam and you’re still encountering the same kind of ‘Fatal Error‘, it’s most likely because the security blockade is enforced by a security rule originating from your firewall settings. Several affected users complaining about the same kind of issue have confirmed that in their case, the issue was finally resolved after they uninstalled the overprotective security suite. But before you do that, you should start by manually disabling the real-time protection in your AV settings and seeing if this fixes the issue. Typically, you can do this directly from the tray bar menu by right-clicking on the icon associated with your antivirus. In case you already did this and the problem is still not fixed, follow the instructions below to essentially uninstall the overprotective AVC from your computer in order to prevent it from interacting with the launch of Dungeon Defenders II: If this method was not applicable or you already follow the instructions below and you’re still encountering the same kind of issues, move down to the next potential fix below.
Method 4: Verify the integrity of Dungeon Defenders II via Steam
According to several affected users, you can also expect to see this issue if you’re currently with some type of corruption-fueled inconsistency that is affecting the local Steam installation of Dungeon Defenders II. If this scenario is applicable, you can fix the issue by forcing the Steam application to run an integrity check on Dungeon Defenders II – This procedure will automatically scan every game file and replace every corrupted item with a healthy equivalent. Note: Before deploying this particular fix, it’s important to ensure that you have a stable internet connection. Follow the instructions below to trigger an integrity check on the Dungeon Defenders II files: In case you’re still encountering the same ‘fatal error‘ startup prompt even after checking the integrity of the game, move down to the final potential fix below.
Method 5: Modifying the BaseEngine.ini File
As it turns out, you can also expect to see the ‘Fatal error‘ to occur when launching Dungeon Defenders II due to a graphics technology that is unable to force Shaders on Demand in situations where the game is rendered on a low-end PC configuration. Fortunately, several affected users that were encountering this issue have confirmed that they were able to fix the issue by navigating to the location of the game and edited the BaseEngine.ini file from the Config directory. After replacing the value of bInitializeShadersOnDemand from False to True, most affected users have confirmed that the issue was resolved and they were able to play the game normally. Note: In order to be able to modify the .ini file, you will need a competent text editor that opens with admin access. In these types of situations, we prefer to use Notepad++ If this scenario looks like it could be applicable, follow the instructions below to modify the BaseEngine.ini so that it allows the usage of in-demand shaders:
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