Lucius: The Eternal Blade is the eighteenth audio drama for the Horus Heresy Series that was not originally released as part of an anthology or other release. Lucius: The Eternal Blade was published online in December 2013 by the Black Library as a part of the 2013 Holiday Advent Calendar, on day number 21. The title was also published as part of the Legacies of Betrayal main series anthology novel.