All That Remains (The Horus Heresy)

As Horus' rebellion consumes the galaxy, the dead number in the billions. Far greater, however, are the countless casualties evacuated from front line duties to tend their wounds and someday return to the fight. On one particular vessel cast adrift in the warp, a handful of ragged Imperial Army soldiers make a startling discovery, and the question of why so many more of their comrades have been lost is soon answered... Read it because
Get ready for a mystery like no other. A derelict ship harbouring sick and dying men gets caught up in a secret mission straight from the Emperor's right hand man, Malcador, to create a new army to save the Imperium. Too bad the citizens on board don't know that. This story is a fascinating revelation about the birth of the Grey Knights and exactly how the seeds of their Chapter were sown.