The class had three variants. The D18A entered service in the late 2250s decade, on reference stardate 2/0108, D18B in the mid-2260s on 2/1110, and D18C in the early 2270s on 2/1803. (FASA RPG module: Klingon Ship Recognition Manual)
Circa 2267 on reference stardate 2/0804, three D18A variant Lara'atan-class ships served in a Klingon squadron that was part of Battle Group 10 and fought in The Romulan Incident in the Triangle, some of which were destroyed during the battle.
By the early 2270s, on reference stardate 2/1512, all 231 D18As constructed had been refit to D18B specifications, with 62 destroyed, 4 captured, 3 scrapped, 3 sold, and 2 reported as missing. (FASA RPG module: Klingon Ship Recognition Manual)
In 2274, Captain Kresz sutai-Kargon commanded a group of six D18-class ships during a raid on a Federation outpost in the Orion Sector. When the starships USS Kongo, USS Halk, and USS Rome arrived in response to the outpost's distress call, Kargon's forces destroyed the Starfleet ships Halk and Rome losing only two of his ships in the process. (FASA RPG module: Star Trek IV Sourcebook Update)
- The timeline in the Star Trek IV Sourcebook Update claims the Kongo was destroyed as well when it engaged the Klingons. Unless another starship were assigned the name, the Kongo wouldn't have been able to participate in the novel Shell Game or in Operation: Retrieve.
As of reference stardate 2/2306.07, the D18B was produced in shipyards at Iosia and H'renn. 358 D18Bs had been constructed, with 82 destroyed, 9 captured, 4 missing, and 2 used as training vessels. The D18C was manufactured at shipyards at Fonawl, Mustaka and Taamar, with 82 built, 4 destroyed, 2 sold, and 1 missing. (FASA RPG module: Klingon Ship Recognition Manual)
IKS Protector • IKS Dark Hand (D18B) • IKS Defender (D18B) • IKS Ganh Wusav (D18B) • IKS Hunter (D18B) • IKS Kaxfiw (D18B) • IKS Ky'jecum (D18B) • IKS Marauder (D18B) • IKS Plunder (D18B) • unnamed Lara'atan-class starships