Cypher: Guardian of Order is the nineteenth audio drama for the Horus Heresy Series that was not originally released as part of an anthology or other release. Cypher: Guardian of Order was published online in December 2013 by the Black Library as a part of the 2013 Holiday Advent Calendar, on the last day. The title was also published as part of the Legacies of Betrayal main series anthology novel.
For a select few amongst the I Legion, the Northwilds of Caliban hold a particularly dark secret. At the command of Luther himself, young Librarian Zahariel accompanies the Lord Cypher on one of his mysterious forays into the unknown depths. But an ancient evil is stirring once more and, with rumours of galactic civil war creeping back to their homeworld, it may have already sunken its claws into the Dark Angels Legion...
- Cypher: Guardian of Order (Audio Drama) by Gav Thorpe