Descent was originally released by Parallax Software in 1995. It was the first game featuring a full 3D environment (before Quake) as well as gameplay that allowed six degrees of freedom and multiplayer networking that allowed players to join and leave at any time.
The resource files from a registered copy of Descent (updated to v1.5) are required. The required files are called DESCENT.PIG and DESCENT.HOG and must be placed in the /apps/descent/ directory. The resource files from the shareware version or the "Destination Saturn" release are not suitable. The game will perform checksum verification at startup to make sure they are correct.