Sons of Fenris is the fifth novel in the Space Wolf novel series, and the first in the series written by Lee Lightner. It was first published in 2004.
When reports reach Terra of a Chaos incursion on Hyades, Ragnar Blackmane and his Wolfblade brothers are sent to investigate. But once there, they find that all is not what it seems. The Dark Angels, ancient rivals of the Space Wolves, are present and eager to allow old feuds to come to the fore. When both Chapters call in reinforcements, the situation quickly escalates out of control – and there is still the threat of renegades and traitors waiting for them...
Accompanying their Navigator charge to Hyades, Ragnar and his comrades are drawn into a plot by the Thousand Sons to foment war between the Wolves and their traditional rivals, the Dark Angels.