The Deathwatch are a unique and specially trained Space Marine Chapter that dedicates its every hour to hunting xenos.

They are the Chamber Militant of the Ordo Xenos, charged with protecting it in its search of information, containment, and ultimate destruction of all xeno species.

Rather than following the standard Codex Astartes organization, the Space Marines themselves are drawn from many different chapters.

(information taken from lexicanum.com)

Players in the Deathwatch are all using Space Marines with the same army painter scheme and the Deathwatch banner, but each player uses the chapter of his choice and with it its unique badge and colour for his shoulder pads.

New divisions will be added when new members join, if their favourite Space Marine chapter is not there.