The file is part of the system introduced in Unreal Engine 4.26 and 5. To work correctly, it typically requires three companion files in the same folder: .ucas : The actual asset data (the largest file).
: While standard Fortnite files are named pakchunk[Number]-WindowsClient.ucas , files with "SaturnClient" in the name are generated or modified by Saturn Swapper . pakchunk20-SaturnClient.ucas
: The .ucas (Unreal Content Addressable Store) extension indicates a "container" that holds compressed game data like textures, models, or audio. The file is part of the system introduced in Unreal Engine 4
: The "Table of Contents" used by the game to find specific items within the .ucas . pakchunk20-SaturnClient.ucas