Install the mod into your main Dow II retribution folder. Readme file included with Credits and instructions. Run either with Astartes.bat, or go to your Steam, go to Retribution, go to Properties, set launch options as "-modname Astartes" ,without the ""s. I recommend setting graphics to Ultra high before installing or mod may crash on space marines. Races , tactics, and units: Space marines heroes all have a separate race attached. Chapter commander is Adeptus Astartes, unlocking the contemporary 40k Space marines. Legion commander is Legiones Astartes, unlocking the 30k era late Great Crusade Space marines. Grey Knights commander is Daemonhunters, unlocking the Grey Knights. IG heroes are the same: Cadian commander unlocks the standard IG. Krieg commander unlocks the Krieg IG. Not suppressible, but fire slower if more powefully with their lasguns. Tau commander: Tau race, similar a bit to IG. Very weak in melee, but good at range due to all of its weapons being plasma or melta.