At the byte level, a PlayStation 4 .pkg file begins with a standard header that acts as a map for the operating system (Orbis OS) to parse the contents. The header is generally found in the first 0x800 to 0x1000 bytes of the file.
Inside the .pkg, after the header, lies the PFS Superblock. This structure contains: bloodborne.pkg
The bulk of the file. For Bloodborne:
.param (FromSoftware’s proprietary data tables) for weapon stats, enemy placement, item drops, and map collisions.