A Son's Burden (Black Library Advent Calendar 2014 #9)

The Blood Angels call for aid, and the Flesh Tearers answer, but Gabriel Seth's warriors are already engaged in battle against traitorous cultists on the dark world of Nekkaris. As Seth and Chaplain Appollus prepare to leave for the Cryptus system, Sergeant Eschiros and his Scout squad fight behind enemy lines, unaware of the almighty sacrifice they may soon have to make... Read it because
The Flesh Tearers are thought of as savage butchers (and there's a bit of that in this book, admittedly) , but this story reveals a deep loyalty and nobility hidden beneath the mask of rage – a link back to their origins on ancient Baal.