Sith dreadnaught

In 5000 BBY, two Sith dreadnaughts, Harbinger and Omen, were mining Lignan ore on a moon of Phaegon III for use in the upcoming Battle of Kirrek, when they were ambushed by Jedi Master Relin Druur and Druur's apprentice, Drev Hassin. Hassin sacrificed himself by crashing the Jedi's Infiltrator starfighter into Harbingers bridge, causing the dreadnaught to crash into Omen right as the two ships jumped into hyperspace. This caused the Omen to crash-land on the remote world of Kesh, where its survivors formed the Lost Tribe of Sith, while the Harbinger entered an unstable hyperspace tunnel and traveled through time to 41.5 ABY. The latter was shortly after destroyed by Druur.

Sometime between 3959 BBY and 3956 BBY, a Galactic Republic-allied Zabrak mercenary raided one of these capital ships. He completed his mission aboard the starship and escaped, but feared for his life, purchasing a heavy, unique suit of battle armor to protect himself from Sith assassins that might be after him.

Around 41.5 ABY, the Lost Tribe of Sith, with the help of Ship, a Sith Meditation Sphere, began to form a Sith armada, and managed to repair the Omen for use in their fleet.