Aaron Dembski-Bowden
Prince of Crows

Sevatar and the Kyroptera try to salvage what they can from the disastrous Thramas Crusade, unaware that their primarch Konrad Curze still lives in a wandering, deathless state.
The Horus Heresy
short

Also in:
The Horus Heresy: Nine Traitor Primarchs
Shadows of Treachery