As the name might suggest, Hollow Knight Multiplayer (HKMP) is a multiplayer mod for the popular 2D action-adventure game Hollow Knight. The main purpose of this mod is to allow people to host games and let others join them in their adventures. A few of the core components of this mod are heavily inspired from an existing implementation found here. However, as it seemed to be discontinued, I decided to rework it entirely and add extra features where possible.

The mod works through the Hollow Knight Modding API (a getting started guide can be found here). After installing the API, this mod can be installed by dropping the compiled DLL into your mods folder, which can be found in your Steam installation: <steam>\Hollow Knight\hollow_knight_Data\Managed\Mods\. The latest version of the compiled DLL can be found on the releases page. The only prerequisite for this mod to work is ModCommon.dll, this can be found in the official ModInstaller or on their Github page. The DLL for ModCommon should also be placed in your mods folder.

The main interface of the mod can be found in the pause menu in-game. There is an option to host a game on the entered port and an option to join a game at the entered address and entered port. Playing multiplayer with people on your LAN is straightforward, but playing over the internet requires some extra work. Namely, the port of the hosted game should be forwarded in your router to point to the device you are hosting on. Alternatively, you could use software to facilitate extending your LAN, such as Hamachi.

The interface can also be hidden by pressing a key-bind (right ALT by default). This key-bind can be changed in the config for the mod, which can be found at the following locations depending on OS:

• Windows: %appdata%\..\LocalLow\Team Cherry\Hollow Knight\HKMP.GlobalSettings.json
• Mac: ~/Library/Application Support/unity.Team Cherry.Hollow Knight/HKMP.GlobalSettings.json
• Linux: ~/.config/unity3d/Team Cherry/Hollow Knight/HKMP.GlobalSettings.json

The key-binds are stored in integer form, to find which key corresponds to which integer, please consult this gist.

The interface of the mod also contains a settings menu. Note that this menu is entirely server-sided, only the player hosting the server will be able to alter the settings. Moreover, the settings will only update server and client-side once the "Save settings" button is pressed.
An explanation of the settings can be found below:

• Enable PvP: whether player vs. player damage is enabled.
• Enable body damage: whether contact damage is enabled, namely when player models touch, both of them will be damaged. This only has effect if PvP is also enabled.
• Always show map locations: whether player's map locations are always shared on the in-game map.
• Only broadcast map with Wayward Compass: whether a player's map location is only shared when they have the Wayward Compass charm equipped. Note that if map locations are always shared, this setting has no effect.
• Display names: Whether overhead names should be displayed.

The rest of the settings contain entries for damage values of most PvP enabled spells and abilities. Inputting a value of 0 will completely disable the damage.

You can also join the Discord server for the mod. There you can also leave your suggestions and bug reports or generally talk about it. Moreover, the latest announcements will be posted there.

HKMP can also be built from scratch. This requires a few dependencies from the Hollow Knight game and the modding API. Namely, the following dependencies should be added as referenced assemblies from the modding API:

• Assembly-CSharp.dll (modified by the modding API)
• ModCommon.dll

And the following assemblies should be added as references from the Hollow Knight game/Unity:

• PlayMaker.dll
• UnityEngine.AudioModule.dll
• UnityEngine.CoreModule.dll
• UnityEngine.dll
• UnityEngine.ImageConversionModule.dll
• UnityEngine.ParticleSystemModule.dll
• UnityEngine.Physics2DModule.dll
• UnityEngine.TextRenderingModule.dll
• UnityEngine.UI.dll
• UnityEngine.UIModule.dll

After this the source code can be compiled into DLL, and you should be good to go!

If you have any suggestions or bug reports, please leave them at the issues page. Make sure to label the issues correctly and provide a proper explanation. Suggestions or feature requests can be labeled with "Enhancement", bug reports with "Bug", etc.

If you like this project and would like to donate, you can do so via Paypal. Please only donate if you really want to, there's no obligation in doing so.