The Eleventh Tome of Klavek was a Klingon mythological text, part of the paq'batlh. It tells the story of Kahless descending into Gre'thor, to rescue his brother from the Barge of the Dead and deliver him to Sto-vo-kor. When he returned, he still bore a wound from the afterlife, "a warning that what he experienced wasn't a dream".
After experiencing a vision of the Barge of the Dead due to an injury in 2376, B'Elanna Torres researched this Tome and believed that the vision was telling her that she must go rescue her mother Miral, before she passed through the gates of Gre'thor. (VOY: "Barge of the Dead")