This tutorial goes over using Nucleus Co-op with a script by Talos91 to allow for multiple instances of Hollow Knight on the same PC, and how to use HKMP to connect those instances into the same server. Note that Nucleus Co-op can only be used on Windows.

Installing the multiplayer mod

This tutorial assumes you already installed the HKMP mod following the steps from the main article. If you haven't, do so before proceeding.

Issues with Nucleus

This version of Nucleus is pretty new. If you find bugs that prevent you from using it properly, check if your issue is addressed in the FAQ section, and if that fails ask in the Nucleus Discord.

First-time installation of Nucleus

• Download Nucleus Co-op. If your anti-virus or browser gives warnings about it, it's a false positive and you will want to ignore warnings or whitelist Nucleus if needed
• Extract the zip with the password nucleus
• Open NucleusCoop.exe
• Click Download Game Handler in the top
• Search for Hollow Knight
• Select Hollow Knight and click Download

• You will be prompted to select Hollow Knight's .exe file, in the game's folder. The folder is located in different places depending on the store you purchased the game

  • Steam: C:\\Program Files (x86)\\Steam\\steamapps\\common\\Hollow Knight

    If you moved the Steam folder somewhere else, you can right-click Hollow Knight on Steam, click Manage, then click Browse local files to see where it is located

  • GoG: Click the symbol next to the play button > Manage Installation > Show Folder, to see where the folder is located

Starting the split-screen script

• Click onto Hollow Knight in Nucleus Co-op's game list in the left
• Select how you want the screen to be split by the script, and which controllers will be assigned to which section of the screen
• Click the right arrow at the top-right, and choose whether you want the Letterboxing fix (removes the black bars in unusual screen sizes)
• Click Play