RICHARDSCOAT83

meant to say Gamestop app, not Origin

Hi guys. I have the first three releases of SINS; Original, Entrenchment and Diplomacy. These were all on the old distro system (I cant remember what it was called before Gamestop bought it). I had all my games swapped over to Origin. My question is, is Rebellion a Steam only release and if so do I need the other games to play it? Thanks guys.