What kinds of lore and advice does the book offer Deathwatch members on fighting xenos?
Deathwatch is a unique aspect of the Space Marine organization within the Warhammer 40K universe. It is a task force composed of Space Marines from various Chapters, often detailed to deal with threats that are too alien, too strange, or too powerful for a single Chapter to handle alone. These threats usually involve xenos (alien) species, Chaos corruption, or other extreme dangers. Warhammer 40K - Deathwatch - Mark Of The Xenos.pdf