Sildur: Hey, awhile ago I made a guide on the steam forum on how to get multiplayer up and running. But the same should also apply to the GOG version. Simply skip the part with the GOG exe file, and maybe you don't need to rename the files. My guide can be found here: EDIT: Cant link it on GOG.

But here's the full post again, edited for the gog version:
After modding NWN2 all day and trying too fix the issues of the Client extension mod, I finally got everything working.

Requirements:
Client extension mod: nwn2dev.blob.core.windows.net/nwn2/ClientExtension_Latest.zip
Aside from multiplayer the extension mod fixes various issues like the stuttering camera during movement.
Getting your keys: "This game may require additional serial key for multiplayer mode. In case it is not automatically generated in your GOG.com library (open it via website → select the game → More → Serial Keys)"

1. Download Client extension mod and extract ClientExtension.hdl and NWLauncher.exe into your NWN2 folder.
2. Create a new file in your game folder and name it nwncdkey.ini with following content:
[CDKEY]
Key1=
Key2=
Key3=
3. Fill in the keys from your gog version, see notes above.
4. Launch the game by running NWLauncher.exe.
5. Click on Multiplayer, type in any username you like in "Bioware community name" and use any password then hit sign in.
6. It will say failed to connect to master server but you should now have access to all the multiplayer options.
7. That's it have fun playing!

Let me know if you have any issues or need help with something.

Nemesis100000000: Hello Sildur.

As of this time of writing, is the online co-op, with your method or another, still working? I am asking because me and 3 friends of mine are considering buying this game mostly for the chance of playing online co-op on its campaign.

Furthermore, even if online co-op campaign is indeed possible, what characters do players control? Does the host control the main character and the other players use the standard party members or can all 4 of us make different custom characters and join the adventure?

Thank you in advance and I look forward to your responses. Any further info will surely be appreciated!

Sir_Will_The_Okay: Yes, I just applied it and I'm able to see servers in Join Internet Game.
Not that I tried to, no one seems to be running the main game.

Sildur: Hey, awhile ago I made a guide on the steam forum on how to get multiplayer up and running. But the same should also apply to the GOG version. Simply skip the part with the GOG exe file, and maybe you don't need to rename the files. My guide can be found here: EDIT: Cant link it on GOG.

But here's the full post again, edited for the gog version:
After modding NWN2 all day and trying too fix the issues of the Client extension mod, I finally got everything working.

Requirements:
Client extension mod: nwn2dev.blob.core.windows.net/nwn2/ClientExtension_Latest.zip
Aside from multiplayer the extension mod fixes various issues like the stuttering camera during movement.
Getting your keys: "This game may require additional serial key for multiplayer mode. In case it is not automatically generated in your GOG.com library (open it via website → select the game → More → Serial Keys)"

1. Download Client extension mod and extract ClientExtension.hdl and NWLauncher.exe into your NWN2 folder.
2. Create a new file in your game folder and name it nwncdkey.ini with following content:
[CDKEY]
Key1=
Key2=
Key3=
3. Fill in the keys from your gog version, see notes above.
4. Launch the game by running NWLauncher.exe.
5. Click on Multiplayer, type in any username you like in "Bioware community name" and use any password then hit sign in.
6. It will say failed to connect to master server but you should now have access to all the multiplayer options.
7. That's it have fun playing!

Let me know if you have any issues or need help with something.

Sildur: Hey, awhile ago I made a guide on the steam forum on how to get multiplayer up and running. But the same should also apply to the GOG version. Simply skip the part with the GOG exe file, and maybe you don't need to rename the files. My guide can be found here: EDIT: Cant link it on GOG.

But here's the full post again, edited for the gog version:
After modding NWN2 all day and trying too fix the issues of the Client extension mod, I finally got everything working.

Requirements:
Client extension mod: nwn2dev.blob.core.windows.net/nwn2/ClientExtension_Latest.zip
Aside from multiplayer the extension mod fixes various issues like the stuttering camera during movement.
Getting your keys: "This game may require additional serial key for multiplayer mode. In case it is not automatically generated in your GOG.com library (open it via website → select the game → More → Serial Keys)"

1. Download Client extension mod and extract ClientExtension.hdl and NWLauncher.exe into your NWN2 folder.
2. Create a new file in your game folder and name it nwncdkey.ini with following content:
[CDKEY]
Key1=
Key2=
Key3=
3. Fill in the keys from your gog version, see notes above.
4. Launch the game by running NWLauncher.exe.
5. Click on Multiplayer, type in any username you like in "Bioware community name" and use any password then hit sign in.
6. It will say failed to connect to master server but you should now have access to all the multiplayer options.
7. That's it have fun playing!

Let me know if you have any issues or need help with something.

Kelltune: I followed these steps but now it's telling me my Keys aren't working. Do you have any advice on this?

Dr.Fly: Hey there.
Wanted to ask, me and my friend followed your guide yesterday, but hosting a server for our coop campaign doesnt seem to work. Are we doing something wrong or does this work only for official servers? Thanks for the help in advance

Peccabecca: My boyfriend and I followed this guide and multiplayer still doesn't work. We can se other servers, but not the ones we create. We can't join by "Direct Connect" either.