PLEASE NOTE:
This mod is being put on hold for GD version 1.2. Because there is new multiplayer balancing with the new patch, the mod will need to be re-worked. I will post updates as I make progress. If you would like to continue playing Grim Dawn with 5-8 players, please use a backup copy of 1.1.9.8.
I finally got it working! Now we can play our favorite ARPG with more people at once! So go buy a few more copies of the game and gift them to some friends! I am very pleased to make this contribution to the Grim Dawn community. I hope you all enjoy!! 
Very special thanks to GlockenGerda for helping me with the HEX editing! Also thank you to Zantai for giving me special permission to share my modified DLL files! I want to make it clear to everyone that I asked permission to share this, and I was instructed to make my disclaimer “absolutely clear”.
DISCLAIMER: The edited engine.dll is NOT officially supported by Crate Entertainment, and you are using these files AT YOUR OWN RISK! Any time you use a modified DLL file, there are risks involved. Always make backups, and be cautious about downloading files that are potentially harmful to your computer.
Do not assume that because I have been granted special permission to share modified game files on this forum, that you are entitled to the same privilege. I am not liable for any damages done to your computer, nor your copy of the game. I also cannot guarantee that the game will continue to function properly when playing online. These files have only been tested on a LAN / VPN.
Instructions:
In order to play the game bug-free with 6-8 players, you will need BOTH the modified DLL files, and the mods.
Modified Engine.dll files: Simply extract these zips into your Grim Dawn directory and overwrite the original files. I have included backups of the original DLLs in the zip archives. There are zips for both the x86 and x64 versions of the game. If you are unsure which version to use, just extract both. These DLLs change the multiplayer drop-down menu to allow up to 8 players, and increase the available party slots to 8.
6/8 Players Difficulty Scaling MODS (v1.1): Simply extract the zip to your Grim Dawn directory. YES, THESE MODS ARE NECESSARY. They are enabled by selecting a custom game in the main menu. Included are FOUR different versions, so please read the descriptions below.
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3-6players_scaled:
Enemy difficulty goes up when adding 5 and 6 players to the game. The rate of increase is meant to match the same rate from 3 to 4 players. I have not fully tested the balancing in this mod, but it’s likely that it will be very difficult! The mod ONLY works properly if you have 3-6 players! -
3-6players_hp-only:
All difficulty scaling stays exactly the same as it is with 4 players, except for enemies’ health, which increases at a linear rate per added player. This mod will be much easier than the “scaled” mod, but I thought players would appreciate having this as an option. The mod ONLY works properly if you have 3-6 players! -
3-6players_plus1:
For a greater challenge, it increases the difficulty as though you had one extra player in your party. The scaling above 4 players uses the same rate as the “scaled” mod, but +1 player. The mod ONLY works properly if you have 3-6 players! -
5-8players_hp-only:
This is the same as the above 6 player version, but the player slots are shifted to accommodate 8 players instead. Enemy health is increased at a linear rate. The mod ONLY works properly if you have AT LEAST 5 players!
If you find anything really outrageous about the scaling in these mods, let me know, and I’ll make some changes. 
FAQ:
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Q: Will the modified DLL files mess up the vanilla game, or other mods?
A: No, as long as you do not host a multiplayer lobby with more than 4 players, your game should function like normal. However, it is likely that the modified DLL files will be overwritten when the game updates, or if you verify the game files. Also, I can’t speak for online play, as I have not tested it. Ye be warned. -
Q: Can I just skip your mods and play with 5+ players with the vanilla game, or a different mod?
A: You could, but the player and monster stats will be very screwed up! For example: In Ultimate, the game will be broken because the database tables will have rows that are filled with zeros. In Normal and Elite, the multiplayer scaling will use the wrong numbers. You will find that your stats, as well as enemy stats, will be stuck in the wrong difficulty level. It’s a really big mess, and it’s just best to use one of the mods if you plan to play with more than 4 players. -
Q: Does this mean I can’t play Crucible with more than 4 players?
A: Bug-free, you cannot do it. You might still be able to play it, but all the stats will be messed up. However, I have not tested this yet. so I can’t say for sure. Since Crucible is a paid DLC, I cannot legally release a version that merges my mod with it. So for now, I recommend playing the shattered realm in Forgotten Gods, as an alternative. -
Q: Why is there no 5-8players_scaled mod?
A: Sorry, too much work for me to worry about right now. I’ll probably make it later. -
Q: Does the game run slower with more than 4 players?
A: Yes. The devs said that this is the main reason why they kept it to only four. Make sure you all have computers that can handle the extra load. You might need to turn down your graphics settings. I didn’t see any networking troubles in my tests, but you might. -
Q: Is it possible to make a single mod that has the correct scaling for all difficulties with all player counts?
A: No, not that I am aware of. The game is hard-coded to categorize the scaling into groups of 4, to accomodate 4 maximum players. My mods work around this by “shifting” the tables to the right. That means that everything to the left is now incorrect. Thus, you must have specifically 3-6 players or 5-8 players. -
Q: Can you make a mod that supports MORE than 8 players?
A: No not really. Even though the engine.dll does technically support it, it gets really buggy above 8 players. -
Q: Can I merge your mod with another mod?
A: Yes, but please remember that the scaling WILL be screwed up in Elite and Ultimate if you have less than 3 or 5 players! (3-6 and 5-8) Please credit me if you share your mod online.
The multiplayer scaling is handled in 3 files, called “balancingadjustment_mp+difficulty”. If your mod does not already include these files, you can simply pick one of my balancing mods, copy those 3 files from it, and merge them into your mod. -
Q: Will this mod still work with future game patches?
A: Sometimes yes, sometimes no. The DLL files worked with versions 1190-1194, but then stopped working with 1195. I’ll try to update when possible, but send me a message if I don’t get to it quickly enough. I don’t think the “balancingadjustment_mp+difficulty” databases have been patched in a long time, so the mods will probably stay just fine. I know the game is now reaching its final stages of patching, so I’ll try to keep an eye on them. -
Q: Can you please release the HEX line edits so I can modify my own DLL files?
A: I’m not totally opposed to it, but I’m not sure if the devs would be okay with me sharing that kind of information publicly. Either way, I think it’s best to wait until the mod gets some dust on its boots first. In the meantime, just use the provided files.
UPDATES:
2022-04-02: Added a new mod “Plus1” that increases the difficulty as though you had an extra player in your party. Mod file has been updated to V1.1.
2022-05-21: Updated DLL files for game version 1.1.9.5
2022-06-21: Updated DLL files for game version 1.1.9.6
2022-12-25: Updated DLL files for game version 1.1.9.7
2023-06-10: Updated DLL files for game version 1.1.9.8
2023-09-04: Updated DLL files for gamer version 1.1.9.8 (hotfix)
DOWNLOADS:
Grim-Dawn_8-Players_MODS-V1.1.zip (83.4 KB)
Grim-Dawn_8-Players_x64-DLL(1198b).zip (3.6 MB)
Grim-Dawn_8-Players_x86-DLL(1198b).zip (3.0 MB)
Old Versions:
Grim-Dawn_8-Players_x64-DLL(1193).zip (3.6 MB)
Grim-Dawn_8-Players_x86-DLL(1193).zip (3.0 MB)
Grim-Dawn_8-Players_x64-DLL(1195).zip (3.6 MB)
Grim-Dawn_8-Players_x86-DLL(1195).zip (3.0 MB)
Grim-Dawn_8-Players_x64-DLL(1196).zip (3.6 MB)
Grim-Dawn_8-Players_x86-DLL(1196).zip (3.0 MB)
Grim-Dawn_8-Players_x64-DLL(1197).zip (3.6 MB)
Grim-Dawn_8-Players_x86-DLL(1197).zip (3.0 MB)
Grim-Dawn_8-Players_x64-DLL(1198).zip (3.6 MB)
Grim-Dawn_8-Players_x86-DLL(1198).zip (3.0 MB)
.It’s just me and my brothers playing grim dawn.My pc is up to scratch to play with more than 5 players.There’s are not.We also got my one brothers wife to learn how to play arpgs.Her fav isdiablo on switch.She still learning grim dawn because of the different mechanics of the game and the amount of builds you can go.
But I considered the mod to be a success! Future LAN parties will certainly include more Grim Dawn. 
So I went and looked up the numbers, and YES, if you play the plus1 mod with 3 players, it will have the exact same difficulty settings as playing with 4 players normally. In addition, if you are playing with exactly 3 or 4 players, you actually do not need to use the modified DLL files. It did not occur to me that the plus1 mod is useful just by itself, but that makes sense! 