Barge of the Dead

The Barge of the Dead is the name of a mythical ship that resides in the Klingon underworld of Gre'thor. It would dock at the point where the souls of dishonored warriors would arrive. They would board the ship, at which point it would set sail for Gre'thor through a blood red river infested with Kos'karii. The warriors on the ship did not have a peaceful journey as those serpentine beings would attempt to lead the dishonored overboard where they would be lost for eternity.

The ship was commanded by Kortor, the first Klingon, who would guide it to the city of Gre'thor itself, as punishment for destroying the gods of the Klingon people.

(VOY episode: Barge of the Dead (episode))