Fantasy Flight Games announced "Hammer of the Emperor", the first supplement for Only War:
Hammer of the Emperor covers a number of famous regiments from across the Imperium of Mankind, including the swift Attilan Rough Riders, the deadly Tanith First-and-Only, the intractable Valhallan Ice Warriors, and others. It also includes new Home Worlds, new Doctrines, and regimental Drawbacks, both to create these legendary regiments and to expand the options of players and Game Masters creating their own unique regiments. On the subject of creating unique regiments, Hammer of the Emperor includes rules for creating Mixed Regiment formations that allow for Guardsmen from different regiments to serve side-by-side.
Finally, to accompany new cavalry regiment options like the Death Riders of Krieg, Hammer of the Emperor includes rules for Mounted Combat, allowing troopers from Rough Rider regiments to fight from the backs of powerful steeds.
Hammer of the Emperor is full of new options to help players overcome the odds on the harsh battlefields of the far future, and I'm very excited to hear about the characters, regiments, and stories that people create with it.
Steel Your Nerves, Guardsman! Hammer of the Emperor is coming late in the first quarter of 2013, but in the meantime, check back for updates and further announcements.
Link: Fantasy Flight Games