In Ubisoft's Dunia engine, data is stored in pairs. The file acts as a file allocation table (an index), while the .DAT file contains the actual raw data.
💡 Always backup the original .fat file before attempting to unpack or modify, as a single byte error will cause the game to crash on startup. If you'd like to dive deeper into the technical side: Specific extraction commands for Gibbed tools. Steps to convert the audio to MP3/WAV. How to repack files for custom mods. In Ubisoft's Dunia engine, data is stored in pairs