Perpetual is the thirty-ninth audio drama for The Horus Heresy series that was not originally released as part of an anthology or other release. Perpetual was first released as an audio drama in December 2016 as part of the Black Library's 2016 Advent Calendar, on day 1. The title has since been released as part of The Burden of Loyalty main series anthology.
Oll Persson stands apart from the rest of Mankind. He is one of the old ones, one of the undying. One of the Perpetuals. Now, fleeing from the ruins of Calth with his band of fellow refugees, the vagaries of the Warp have brought him through the backways of time and space to a city that rests on the edge of oblivion...and no further. The path has ended abruptly, and Oll's enemies are finally closing in. Will his immortality be enough to save him this time?
- Perpetual (Audio Drama) by Dan Abnett