A multiplayer mod for "Hogwarts Legacy" is a modification made to the game that allows multiple players to connect and play together in a shared online world. This means that players can team up, compete against each other, or explore the magical world of Hogwarts together with friends or strangers. The mod typically requires the installation of additional software or files, and may involve connecting to a server hosted by the mod creators or other players. Once connected, players can communicate with each other via chat or voice, and interact with the game world in real-time. However, it's important to note that "Hogwarts Legacy" does not currently have an official multiplayer mode, and any third-party mods that enable multiplayer may be unsupported and potentially risky to install.