The Shadowmasters is the seventeenth short story published in the Horus Heresy that was not originally part of an anthology novel. The Shadowmasters was originally published inside of the dust jacket for the hardcover edition of Corax: Soulforge. It was later released as an audiobook (MP3). It is also now included in the Corax anthology novel and in the Echoes of Imperium audio anthology. The cover art shown is from the audiobook edition, as the story was never released as a stand-aone e-book.
The Mor Deythan stand apart from their brothers of the Raven Guard Legion -- indeed, there are many who would claim that they do not even exist. Blessed with the same powers of stealth and subterfuge as their Primarch Corvus Corax, the self-styled Shadowmasters may slip through any battlefield, unseen and unheard, until they are ready to strike. Now, as the Legion mounts its attack on the forge-temples of Atlas, Brother-Sergeant Chamell leads his warriors on a vital, clandestine mission to strike at the enemy's heart.
- The Shadowmasters (Short Story) by Gav Thorpe