various
Sons of the Emperor: An Anthology
Primarchs (series)
The primarchs, nigh-immortal sons of the Emperor of Mankind, are laid bare in a series of short stories that showcase great deeds and hideous acts they performed, from the Great Crusade and the Horus Heresy.
The Horus Heresy
anthology

It contains:
Prince of Blood
Shadow of the Past
Mercy of the Dragon
The Ancient Awaits
Misbegotten
The Abyssal Edge
The Passing of Angels
The Emperor’S Architect