The Xyntas-class Cruiser was a special warship of the Lost Ones navy. Only one known vessel of this type, the Acheron, was thought to have been built. The vessel was used to strike fear into the hearts of the Lost Ones' enemies. The largest ship in the Lost Ones' navy, the ship harassed larger shipping lines, but was mainly used as a symbol of fear. This was until the Lost Ones came into conflict with the Muir. They needed the vessel to effectively fight against the much larger Muir navy. Over time, it racked up an impressive number of kills against the Muir, until it was eventually bested and destroyed.
The Muir have the blueprints for the vessel. However, upon examining the design, the Muir were left wondering how the Lost Ones managed to keep the ship running, and the design was riddled with flaws throughout. A large portion of the Lost Ones' supplies had gone in to maintaining the ship, particularly the reactor, for the number of things required of it. Despite having the abilities and the resources to better maintain the design, the Muir felt that it was better that all vestiges of the Lost Ones be stamped out, to eliminate their memory in the people of the Ogriand Sector's minds. As such, they retired the design.