According to the post, Knights Armiger are smaller Knights piloted by bastard children of Barons and Knight nobles...well, I'll just copy and paste here.
Smaller than their cousins and crewed by aspiring nobles, low-born commoners with a knack for war, or even the bastard children of Barons and High Kings, Armigers hunt and fight at the flanks of their larger kin. Knight Armigers will open up new tactical possibilities for Imperial Knights players, like a medieval lord hunting with his hounds, benefiting from a wider range of army builds.
That sounds awesome! I'll keep an eye out for this guy and add him to my collection! Right now, my Knights are pretty expensive, especially when I want to add allies, so swapping one Knight for one of these guys would allow me to open up more tactical possibilities and leave more room for allies (looking at you, Adeptus Mechanicus). I'm still waiting for Imperial Armor: Fires of Cyraxus, which is rumored to be released in March and if possible, I want to run an Imperial Knight army with Legio Cybernetica allies. Furthermore, I'm planning on throwing in a Spearhead Detachment (Leman Russ tanks) alongside my Knights if this new Knight Armiger is cheap enough for me to do so.
Just look at that guy! He looks so awesome! WOOHOO! I can't wait! I hope he's a Lord of War too, maybe about 200-300 points, because that will greatly help me and open up more space for allies!