When the Empire developed a working gravity well projector, it was determined that a special vessel would need to be constructed to provide the necessary power output the device required. So the Interdictor-class Heavy Cruiser was designed by Sienar Fleet Systems.
The gravity well generator works on a simple principle. When focused, it sends out waves of energy that disrupt mass lines in space, thereby simulating the presence of a large stellar body such as an asteroid or planetoid. The presence of so much mass prevents ships in the area from engaging their hyperdrives, and it also drops ship already in hyperspace back into realspace.
The Interdictor Cruiser serves as an escape cut-off, strategically stationed out of direct combat, but in a position that provides a maximum fire arc. It projects fields of gravity throughout a battle zone, rendering all hyperdrives inoperable. This greatly reduces the chances of Rebel ships, which normally survive by using quick hit-and-run tactics and then escape into lightspeed.
These Heavy Cruisers also perform as ambush vessels, hiding along known hyperspace lane and projecting gravity fields that produce mass shadows. Any ships traveling along the hyper route must slip back into realspace when confronted with gravity projections. Once in realspace, other Imperial vessels can engage them in direct combat or board them for customs inspection. | 
