To try and keep the game balanced, the XP gain and item quantity have both been halved, (Must be in the normal difficulty)
To install the mod, simply extract the file, and place the folder "Umbra" in your "Game" folder inside your Wolcen install folder.
The "Game" folder is the one with all the .pak files, just put the "Umbra" folder there, and have fun.
If you run into bugs or something let me know, I did not test all the possible spawns etc. Also be warned, the game is quite challenging, if you don't cheat ;)
If you want to make it even harder, you can edit the file in "DifficultyMode" folder with a text editor, and change the multipliers, its quite straight forward for that part.
Now, if you want to increase the amount of enemies even further, well, you could edit all of the other files in the other folder, and change the "NumberMin" and "NumberMax" to whatever you like, "NumberMin" being the minimum amount of that specific enemy per spawn, and "NumberMax" is the maximum.
I recommend trying this mod with a new character, but feel free to use as you wish.