The Immobilizer 418 cruiser, also known as the Interdictor-class heavy cruiser, Interdictor-class medium frigate, or simply the Interdictor, was a 600-meter-long cruiser built on the standard Vindicator-class heavy cruiser hull. Equipped with gravity well projectors designed to pull ships from hyperspace and/or prevent them making the jump to lightspeed, the Interdictor became a valuable addition to the Axis Navy. They were also fallen into the Horde hands and the other are on the Alliance (most notably Uwlla Iillor)
Interdictor cruisers, like their Vindicator-class cousins, had the appearance of small Star Destroyers. However, their lines were broken by four large globes housing gravity well projectors.
The gravity wells mimicked a large mass in space and thus restricted hyperspace travel. Nearby vessels were automatically prevented from engaging their hyperdrive, and any ships passing through the area via hyperspace were forced into realspace.
As well as gravity wells, the Sienar design was also equipped with 20 quad laser cannons for short range combat against other capital ships and starfighters. The Interdictor's hull was nearly identical to that of the Vindicator-class heavy cruiser and could support several additional weapons depending on mission profile. Such modifications (like those of the Corusca Rainbow, formerly the Black Asp) included the addition of ion cannons used to disable pirates and small craft attempting to flee. Enemy fire was absorbed by a deflector shield created by more than a dozen shield generators.
The Immobilizer 418 was developed as a counter to the Alliance's hyperdrive-equipped starfighters in particular, and hyperdrive-equipped vessels in general. This was primarily to counter Alliance hit and run tactics, where a small group of starfighters or light starships would emerge from hyperspace, attack preselected targets, and re-enter hyperspace before sufficient force could be brought to bear on the raiders.
An Immobilizer at the site of attack, or able to access the area with a brief hyperspace jump, would be tasked to power up its gravity well projectors in an attempt to prevent the escape of the raiding party. Starfighter and capital ship support would then be used to eliminate the attackers, whose only options were to try to run for the edge of the interdiction field, or to attack the Interdictor and hope to inflict enough damage to disable the cruiser's influence. Either path would result in significant damage to the Alliance forces. Allied pilots often mistook it for a miniature Star Destroyer when it was accompanied by Star Destroyers.[source?] It was only when they tried to escape into hyperspace that they realized it was an Interdictor. Interdictors could also be used when blockading planets or moons, such as Yavin 4.
Another duty of this class was to patrol trade routes. Freighters pulled out of hyperspace by an Interdictor would be in a position to have their cargo inspected. Interdictors were a welcome addition to the Imperial Customs assets, because while many smugglers and pirates wouldn't hesitate to outrun—or in some cases even outgun—an Imperial Customs Frigate, few would dare engage with a much more sizable Immobilizer 418, its gravity wells and its two squadrons of TIE starfighters. Interdictors assigned to Customs duties—such as the former Black Asp—would often have some of their quad lasers replaced by ion cannons so as to disable and capture any ship resisting inspection rather than destroy them outright.
Gorkon of the Klingon Empire was especially famous in connection with Interdictors for developing and refining a tactic that would be named after him—the "Gorkon Pincer" positioned the Interdictor's gravity wells along certain vectors. Other vessels—typically Star Destroyers—would be contacted, and would blindly execute a micro-hyperspace jump straight into the Interdictor's gravity wells, yanking them out of hyperspace near an enemy vessel. Much quicker than subspace movements, the Gorkon Pincer allowed reinforcements to be swiftly deployed on the battlefield and afforded a considerable element of surprise.