The Book of the Grave-War an eschatological text supposedly written by a German Malkavian in the 12th or 13th century concerning Gehenna and diablerie. However, one source says book was penned by the ancient Jacob under the guidance of a vampire "more adept in manipulation and control than any other". It was translated and studied by Dr. Mortius and later ended up in the hands of Carna, due to the manipulations of Jacob's alternate personality Esau.
Characters who take the 5th level of the Carna Loresheet gain access to the book, which grants them an automatic success on Occult rolls related to the Gehenna and breaking one's Blood Bonds. The character becomes unbondable so long as they follow its arcane teachings, but become hunted by clan Tremere and also become increasingly paranoid.
References
VTM: Milwaukee by Night, p. 52
VTM: Vampire: the Masquerade 5th edition corebook, p. 385
VTM: Becket's Jyhad Diary, p. 19