While the game was originally on Xbox 360, the PS3 version (released later) came with specific content that was not available on the Xbox disc version (though some was later added as paid DLC on Xbox).
The rise of RPCS3, the PS3 emulator for PC, has given new life to the Castlevania Harmony of Despair DLC PKG Exclusive concept. On RPCS3, you can drag and drop the PKG files into the emulator’s directory, drop the RAP file into dev_hdd0/home/exdata, and the game runs at 4K resolution with all DLC unlocked.
Just remember: if you are installing PKGs manually, check your region code. There’s nothing worse than installing a 2GB file only to have the game look at you with the silent indifference of a save file that "Cannot Find Content."
The exclusivity of the DLC package was a major draw for players, as it offered a unique experience that was not available to players on other platforms. For example, the PlayStation 3 version of the game included exclusive content, such as the "Requiem for the Dead" DLC package, which was not available on the Xbox 360 version. This exclusivity was a major selling point for players, as it offered a unique experience that was tailored specifically to the PlayStation 3.
Dive into the ultimate gothic action with the Castlevania: Harmony of Despair DLC PKG Exclusive — a limited digital bundle that expands the co-op metroidvania experience with new stages, playable legends, and exclusive skins. This PKG includes:
(HoD) features a significant amount of DLC that expands the character roster and level count. While most content is eventually shared between platforms, the PS3 version (often found as a "Full Game" PKG) includes some DLC as part of the base experience that was sold separately on Xbox. PS3 vs. Xbox DLC Comparison