Korok's ship was a Klingon D5-class tanker variant in service during the 2150s. Unlike the standard D5 class battle cruisers, the ship appeared to be little more than a freighter and was thought to be no match for an NX-class starship.
Under the command of Korok, the vessel arrived at a deuterium mining colony each season, at which time Korok and his men would forcibly take most of the deuterium that Tessic and his people had mined, leaving them with very little. This exploitative relationship came to an end in 2152, when the colonists, with assistance from the crew of Enterprise NX-01, learned to fight back and successfully drove Korok and his men off the planet. (ENT: "Marauders")
Coined the "Klingon D5 Class Tanker" in production staff circles, the vessel was designed by John Eaves and built as a CGI model by Pierre Drolet at Eden FX. [1](X). [2]
"Marauders" marked the episode in which the model debuted. Neither class nor its designation as "tanker" were specified in the episode and it appeared only in this episode as such. The model made three subsequent appearances without the tanks as a battle cruiser, the first time in "Judgment", where it received its class designation.