Dan Abnett
Eternal

Captain Froer of the Astra Militarum and his men receive a new ally in their attempts to push into enemy territory – a Space Marine of the Blood Angels Chapter. But as Brother Gammarael wages war with a monstrous foe, Froer gets a glimpse of the eternal darkness that lurks at the heart of the sons of the Angel.
Warhammer 40k
short

Also in:
Lord of the Dark Millennium
Sons of Sanguinius: the Blood Angels Digital Collection