ISO files are digital "images" of physical discs. In the early 2000s, these were necessary to bypass CD checks or to install the game on devices without optical drives. Diablo® II Lord of Destruction® (2001) - Battle.net
If you specifically need original disc images (ISOs) for preservation or specific version modding (like version 1.09 or 1.10), community-run archives host these files: diablo 2 lod iso link
Preserving the original 1.00 or 1.07 versions that aren't available on Battle.net. ISO files are digital "images" of physical discs
: This is the "golden version" for most modding. If you use the modern Battle.net installer, it will auto-update to it will auto-update to