The release refers to a cracked version of the game released by the warez group CODEX. This specific release package typically included the base game, all previous DLCs ( Flashpoint , Urban Warfare ), and the new Heavy Metal expansion, pre-patched to version 1.8.1.
This version is often considered the "complete" experience for players looking to mod the game, as major total conversion mods like BATTLETECH Extended (BEX) BATTLETECH Heavy Metal Update V1 8 1-CODEX