Gav Thorpe
Path of the Outcast
Path of the Eldar (series) part 3

Reaving his way across the galaxy in a pirate warband, Aradryan crosses swords with many alien foes. When one of them attacks Alaitoc, the craftworld's fate is in Aradryan's hands.
Warhammer 40k
novel

Also in:
Path of the Eldar
Alien Invasion: the Xenos Digital Collection
The Eldar
Paths of the Eldar