You can find the DLC directly on the Party Hard: Dark Castle Steam page.
While some third-party sites list an executable named PartyHardGame.exe , it is highly recommended to use official launchers like Steam or GOG to avoid security risks associated with unofficial .exe files. Technical Tips download-party-hard-dark-castle-the-games-download-exe
It was developed by Pinokl Games and published by tinyBuild. How to Access the DLC You can find the DLC directly on the