From the announcement:
The will of the Emperor sends the Deathwatch through the most deadly regions of space, including the Jericho Reach, where the Deathwatch currently guards the universe as a sword against the darkness. The service of the Emperor is grim and dangerous, and only a few attain the honor of becoming a veteran of the Deathwatch. Those who survive are truly chosen by the Emperor.
The Emperor’s Chosen, a new supplement for Deathwatch, is now available for download at drivethrurpg.com and rpgnow.com! With it, you and your Battle-Brothers can experience the full weight of glory and responsibility laid upon the shoulders of those who have become Deathwatch veterans.