Mark of Calth is the twenty-fifth volume in The Horus Heresy series of novels and is an anthology of short stories.
Mark of Calth takes place during the Battle of Calth and the Underworld War that followed. The Heresy came to Calth without warning. In just a few solar hours of betrayal and bloodshed, the proud warriors of the XIIIth Legion -- Roboute Guilliman's own Ultramarines -- were laid low by the treachery of their erstwhile brothers of the XVIIth Legion, the Word Bearers. Now, as the planet is scoured by solar flares from the wounded Veridian star, the survivors must take the fight to the remaining Word Bearers and their foul allies in the Underworld War, or face damnation in the gloomy arcology shelters beneath the planet's surface. A collection of stories by authors including Dan Abnett, Aaron Demsbki-Bowden and Rob Sanders. The battle for Calth is far from over...
Mark of Calth contains the following short stories:
- The Shards of Erebus by Guy Haley
- Calth That Was by Graham McNeill
- Dark Heart by Anthony Reynolds
- The Traveller by David Annandale
- A Deeper Darkness by Rob Sanders
- The Underworld War by Aaron Dembski-Bowden
- Athame by John French
- Unmarked by Dan Abnett
- Mark of Calth (Anthology) edited by Laurie Goulding