The Lost Ones was a former elite Special Operations squad in the Rakatan Military, which became a Dark Side cult after the group fled to Malachor V.
The Lost Ones were originally formed as the Militisab Cruentus, or the Soldiers of the Void, a special operations group formed by the Rakatan warlord, the One.
The Militisab Cruentus existed primarily as an internal affairs unit, ensuring loyalty to the Rakatan Overlord and quashing uprisings amongst the Empire's enslaved species. The Militisab Cruentus was performing a scouting mission, when the Infinite Rakatan Empire was stripped of its powers due to the Eborax virus, therefore narrowly avoiding its efrects. However, when they arrived at their home world, it was discovered that they still had their connection to the Force and the One ordered that they be detained, dead or alive, in order to design a cure for the virus' effects.
The Militisab Cruentus escaped the Overlord's grasp and were chased to the planet's atmosphere, where they were able to escape pursuit due to the purseur's loss of control over the Force and in extension any Rakatan vehicles. The unit travelled far and wide, eventually establishing a compound on the planet Malachor V. There, the group decided to strip themselves of their previous title, adopting the Lost Ones as a reflection on the their state in the Rakatan Empire. Whilst on Malachor V, the Lost Ones delved into the Dark Side of the Force but later left it for Malachor VII.
During the Cruentusian War, the Lost Ones participated in several minor skirmishes, and succeeded in retrieving the Hand of Darkness artifact. Following their defeat on the desert world of Ahara, which also resulted in the death of their leader Ravyr and the Hand of Darkness falling out of their hands, they retracted from the war.