Looks and Fluff, but also I like to share my interpretation of a faction. I have made three attempts over the years to get into the hobby and this last one seems to have stuck with the new
GW. I loved the new Marines, so ditched my previous two starter armies and dove in with two split Dark Imperium boxes to get a solid core together. Wanted to have an army that was just fringe enough that it would be unique at my local store which is one of the larger ones around, but also mainstream enough to get at least some official support occasionally. I am a decent painter, but didn't want anything too extravagant. Flipping through the codex I ended up being drawn to the Black Templar's. I've expanded with a Repulsor, Redemptor, and a Chaplain, customized a few sergeant models to break up the monotony of the two
DI Boxes and that got the main theme of the army pretty well set. To push the crusading knights theme, and a nod to the old Crusader Squad, and because I think they are so darn cool, I added a full squad of Rievers. For kill team I did another five Rievers in veteran heraldry with some heavy mods. I'm comfortable with the main line plus theme unit approach and like where the army is at for now. Only problem I got is I love the new Shadowspear box and I'm having a hard time justifying it in my army, because gosh darn it I didn't expect them to make a Librarian I'd like and yet here we are