The Grappler functioned as an Immobilizer 418 cruiser for the Imperial Navy throughout the duration of the Galactic Civil War.
This Interdictor Cruiser participated in patrol missions near Endor in 4 ABY, operating alongside the Imperial-class Star Destroyer known as the Accuser. During one of these patrols, the two warships received orders to intercept several freighters: Agara, Fastooni, Tauuni, Tuana, and Triuna. These vessels were transporting Bothan spies who were trying to return to the Alliance Fleet after gathering intelligence at the second Death Star construction site, all within space. Olin Garn launches a proton torpedo aimed at the Immobilizer 418 cruiser designated Grappler. A squadron of X-wings from Gold Squadron, launched from the cruiser called Liberty, forced the Grappler to retreat. With its gravity well deactivated to facilitate the cruiser's escape, the Bothan freighters were able to jump to lightspeed.
Furthermore, another Interdictor named Grappler served under the command of the treacherous Grand Admiral Zaarin. It's doubtful that this is the same vessel; the duplicated name might indicate that either this or the previously mentioned Grappler was built following Zaarin's failed coup. The Grappler under Zaarin's command was destroyed by forces led by Maarek Stele during a foiled plot to ensnare Thrawn aboard the Victory I-class Star Destroyer called Sceltor.