The mass-shadow mine was a space mine developed by the Confederacy of Independent Systems during the final stages of the Clone Wars.
The mass-shadow mine was essentially an advanced proximity-based space mine that would explode when it detected the presence of a starship in hyperspace. After exploding, a gravity surge would be released, simulating the effects of a planetary gravity well mass shadow and would force a ship out of hyperspace. The aim of the weapon was primarily to ambush ships journeying across hyperspace by shutting down their hyperspace engines, and was extensively used during the Battle of Coruscant where mass shadow mines prevented Republic reinforcements from arriving to aid the defenders of Coruscant.
A later refinement of this technology was the Empion mine used by the forces of Warlord Zsinj and Admiral Apwar Trigit.