If you look at the symbols in the teaser you of course got Imperial Fists and Sons of Horus as the HH poster boys, Adeptus Titanicus as that would obviously be usable in epic but you also have two units with what looks like an Imperial Aquila to me on the IF side. That makes me think those could maybe be Custodes? Don't really know that much about HH lore so no idea if anyone else used it as their symbol during that time. But should at least be some faction other than the SM legions