Name: Sienar Fleet Systems Immobilizer 418 Interdictor-class Heavy Cruiser
Manufacturer: Sienar Fleet Systems
Model: Immobilizer 418 cruiser
Type: Cruiser (standard classification)
Cost: 52,240,000 credits (black market value)
Scale: Capital
Length: 600 meters
Width: 300 meters
Height/depth: 100 meters
Skill: Capital ship piloting: Immobilizer 418
Crew: (2,807), Gunners (24), Officers (427), Enlisted (2,380), skeleton: 1,500/+10
Crew Skill: Astrogation 5D, capital ship gunnery 5D,capital ship piloting 5D, capital ship shields 4D
Passengers: 80 troops
Cargo Capacity: 5,500 metric tons
Consumables: 1.2 years
Hyperdrive Multiplier: x2
Hyperdrive Backup: 8
Nav Computer: Yes
Maneuverability: 1D
Space: 6
Atmosphere: 320;975kmh
Hull: 5D
Shields: 3D
Sensors:
        Passive: 30/1D
        Scan: 75/2D
        Search: 150/3D
        Focus: 5/4D
Weapons:
                Quad laser cannons (20)
                Fire Arc: 10 front, 5 left, 5 right
                Skill: Capital ship gunnery
                Scale: Capital
                Fire Control: 2D
                Space Range: 1-3/12/25
                Atmosphere Range: 2-6/24/50 km
                Damage: 4D
        SFS G7-x gravity well projectors (4)
                Fire Arc: Turret
                Crew: 1
                Skill: Capital ship gunnery
                Fire Control: 6D
                Space Range: 1-5/75/150
                Damage: Blocks hyperspace travel

Starfighter Complement:
        TIE/ln space superiority starfighters (24)

Description: The Immobilizer 418 Interdictor-class Heavy Cruiser, also known simply as the Interdictor-class heavy cruiser, Interdictor-class medium frigate, Interdictor Dreadnaught, or simply the Interdictor, and sometimes colloqually as the Drag Ship, was a 600-meter-long cruiser built on the standard Vindicator-class heavy cruiser hull (later used for the Enforcer-class picket cruiser).

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 Imperial Navy.

Characteristics
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 to combat 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.

A variant of the Interdictor design existed, equipped with two large gravity wells rather than the usual four: a ship of this type appeared in Grand Admiral Thrawn's ambush of Luke Skywalker at Jomark in 9 ABY.

Role
The Immobilizer 418 was developed as a counter to the Rebel 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. 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.

Grand Admiral Thrawn was especially famous in connection with Interdictors for developing and refining a tactic that would be named after him—the "Thrawn 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 sublight movements, the Thrawn Pincer allowed reinforcements to be swiftly deployed on the battlefield and afforded a considerable element of surprise.

Weaknesses
Although they were tremendous assets to any fleet, Interdictor cruisers suffered from some drawbacks. First and foremost, it took some time to power up and activate the gravity well projectors after the cruiser positioned itself and, once activated, the tremendous simulated mass they generated made the ship very slow and cumbersome to maneuver. While there was rarely enough time for an entire fleet to make the jump to hyperspace before a newly-arrived Interdictor activated its projectors, fast ships and starfighters could often escape to the edge of an active gravity well, and then make the jump to hyperspace.

The gravity wells were also a large drain on the ship's energy reserves, preventing the optimal use of weaponry and shields. This flaw was exploited on several occasions. When enemy ships were able to inflict significant damage to the Interdictor, the captain was forced to choose between entrapment of the enemy and his ship's own protection. It was further due to this immense power drain that the Immobiliser 418 could not have its gravity well generators perpetually activated, only capable of remaining active for a few hours before a forced-shutdown was instituted, one of the many things which led to the creation of the better powered Interdictor Star Destroyer. This flaw was compounded by the fact that Interdictors were poorly protected and armed for a capital ship of their size. Enemy forces could send a smaller warship, such as an Nebulon-B frigate or Thranta-class War Cruiser to weaken an Interdictor's defenses and quickly force it to power down its gravity wells to fend for itself. Although the abilities of the Immobilizer 418 were fairly effective against the missile launchers of the Marauder-class corvette often employed by the Rebel Alliance, the ship was also known for its notorious weaknesses against larger capital ships such as the Mon Calamari MC80 Star Cruiser and bombers such as the BTL Y-wing starfighter.

Additionally, the engine and hyperdrive-specific areas of an Immobilizer's interior sections were crewed only by maintenance droids, and were totally unprotected. Raiders and saboteurs were thus able to infiltrate and either disassemble or destroy the vital parts of the cruiser's propulsion systems.

Due to their importance and weaknesses, Immobilizer 418 cruisers were usually found on the periphery of the battle they were affecting, escorted by larger and better equipped capital ships and starfighters to protect them from harm and deliver the necessary damage.

Other Interdictors
While Sienar Fleet Systems' Immobilizer 418 was the most common design of Interdictor, other ships made use of gravity well projectors. Kuat Drive Yards used the hull of an Imperial-class Star Destroyer to create the Interdictor Star Destroyer which was supposed to compensate for the Immobilizer 418's combat weaknesses. The command ship used by Darth Vader immediately after the Battle of Yavin mounted large projector globes in the manner of the smaller cruisers.

During the Yuuzhan Vong War, the New Republic launched Mon Mothma and Elegos A'Kla, which carried improved interdictor equipment inside a normal Star Destroyer hull. The immense Eclipse-class and Sovereign-class Star Dreadnoughts also carried projectors internally within their massive hulls.

Interdictor technology was not completely limited to the Empire, however. Alliance forces made use of older CC-7700 frigates, and scientists in the Hapes Consortium reverse-engineered the gravity-well projector from captured ships; but rather than building bulky projectors, the Hapans fitted their Battle Dragons with launchers for charges known as pulse mass mines, which produced much the same effect. However, pulse mass mines could not be turned off or controlled like gravity wells, so this trapped the Hapans in the battle as well.

Service history
The Interdictor cruisers were first manufactured by Sienar Fleet Systems two years before the Battle of Yavin. It was an Immobilizer 418 cruiser named Assessor that boarded Han Solo's Millennium Falcon, forcing him to jettison the glitterstim spice that he was smuggling for Jabba the Hutt and had the Falcon searched by Captain Tybert Capucot before Solo escaped once again from Imperial forces.

Many Vindicator cruisers were converted to Interdictors. In spite of that, only a relatively small number was used against the Rebels.

An Interdictor of the Imperial fleet was essential in the capture of Moff Kalast during the period of the Death Star construction. The Interdictor prevented the traitorous Moff's Star Destroyer from jumping to Hyperspace long enough for the Destroyer to be captured.

An Immobilizer 418 cruiser was responsible for the elimination of the Deretta Destroyers, an Alliance to Restore the Republic starfighter squadron, sometime before the Battle of Hoth. The squadron jumped into the target area of an Imperial depot ahead of their main Rebel strike force, where they softened up the opposition. However, the Immobilizer's presence prevented them from escaping, and the Destroyers were wiped out before the bulk of the Rebel force could arrive.

Between the Battles of Hoth and Endor, the Immobilizer 418 saw extensive action during the campaigns involving rogue Admirals Harkov and Zaarin and the threatened proliferation of TIE Defender technology. Aside from Thrawn, Zaarin was the only other Imperial officer to make frequent use of the Interdictor cruiser. Zaarin had the Harpago try to stop Darth Vader from warning Emperor Palpatine about the coup, then he deployed Grappler to trap Thrawn at the Rebel platform RS-32. In both instances, Zaarin's Immobilizer 418s were destroyed thanks to the intervention of Maarek Stele.

The Immobilizer 418 was produced in very limited quantities prior to the Battle of Hoth. By the time of the Battle of Endor, Sienar Fleet Systems less Interdictors than Imperial Star Destroyers.

An Interdictor cruiser was once used by the Zann Consortium during a piracy mission above Bespin.

During the Bacta War, the Interdictor cruiser Aggregator ambushed Rogue Squadron at Alderaan's Graveyard.

After the Battle of Endor, the one time lieutenant Lon Donell turned to piracy and used the Detainer to raid New Republic shipping.

During the Hunt for Zsinj, Admiral Teren Rogriss moved his flag to the Interdictor Stellar Web and collaborated with Han Solo's fleet to trap and engage Warlord Zsinj's Iron Fist at the Battle of Vahaba.

These vessels would not realize their full potential until several years after Emperor Palpatine's death, when they became a key component in Thrawn's attempt to defeat the New Republic. The Grand Admiral, who commanded a large number of these ships in the Outer Rim Territories, would deploy them to ambush New Republic forces. He once used an Interdictor in conjunction with his flagship, Chimaera, in an attempt to capture Luke Skywalker. However, the Jedi eluded capture, by escaping Chimaera's tractor-beam lock, racing out of range of the gravity-well projector, and making a quick jump into hyperspace.

After Thrawn's defeat, New Republic technicians redesigned the Interdictor's gravity-well projectors, improving both their range and recharge rate. These new Interdictors, designated Immobilizer 418As, became one of the key components of the New Republic Defense Fleet during the Yuuzhan Vong War. During the Battle of Fondor, the New Republic supplied four Interdictors to the Hapan fleet.

One Immobilizer was used with other antique vehicles in the construction of the Hidden Temple used by the Jedi as a secret refuge during and after the Sith–Imperial War, and at least one was used during the Evacuation of Dac.