: The essential piece of hardware. Even after installation, the game required this specific disc to be physically present in the CD-ROM drive to verify you owned the game before it would launch. The Rise of the ISO

When Diablo II first launched in June 2000, it arrived in a massive "Big Box" containing a three-disc set:

As the years passed, the physical "Play Disc" became a liability. Hardcore players found that the constant spinning in high-speed CD drives could lead to wear, scratches, or in rare cases, discs shattering inside the drive. To protect their investment, the community turned to —digital clones of the physical discs.