The search query refers to a pirated/repackaged version of Halo 5: Forge (often mistakenly identified as the full Halo 5: Guardians campaign) distributed via BitTorrent. R.G. Mechanics is a well-known "repacking" group in the warez scene, famous for compressing game files to reduce download sizes.

The game is available for download via torrents from various sources. However, we do not provide direct links to torrent files. Users can search for "Halo 5: Guardians PC Repack by R G Mechanics" on their preferred torrent search engine to find the game.

that has never received a full campaign or multiplayer port for Windows. Why a "Full PC Game" Repack Does Not Exist Port Scrapped : Former developers at 343 Industries

Unlike its predecessors, Microsoft kept it an Xbox One exclusive. What actually exists? The only legitimate piece of Halo 5 on PC is Halo 5: Forge