The PTMC Mining Robots are the foes the player encounters in the Descent series. Originally used for mining purposes, they turned renegade when a computer virus infected them. Now, they seek nothing less than to destroy anyone who enters the mines. Any researchers they confront, they either imprison or do away with. They are sent by Samuel Dravis to prevent the material defender from destroying the mines in which they reside.

The robots use a variety of weapons and defenses against the player, and use them with varying levels of intellect. While some charge head-on, others get very sneaky. Still others have cloaking devices and are nearly impossible to detect. There are even some who sap your energy or steal your weapons.