Captain Arzach is the current force Commander for my Space Marine army. I hadn't originally intended to create the model for my leader until I had most or all of the army already completed (that way , I can work out more of the color scheme, technique and flavor with the less important models). But, the Bolter & Chainsword Space Marine forum was holding a contest for command models! The last time I entered one of their contests, I realized that I work better with deadlines (must have to do with being a free-lancer?). If I don't have a deadline, I find that I will often put a project on the back burner once it becomes frustrating, then get excited about some newer project... and it may never be finished. Another thing I noticed is that the friendly competition with my peers also makes me put extra effort into my work. So, when I heard about another contest... I couldn't resist!

I've found that most of my army's background stories happen while I am modeling and painting. I knew I wanted an interesting base, and what more popular a subject than a fallen enemy? I had a plastic berzerker handy, so it fit the bill! My concern was having a bright red model on the base attract too much attention (red and green being complimentary colors). I had already made the choice for the army's bases being sort an arid motif, so I figured I could tone down the bright red with some heavy weathering and oxidization. Another issue was to not use an entire model on the base, as it would be too cumbersome in game play. So, I made the berzerker half buried in the sand (how'd He get way under there?). This gave me an idea about the chapter having been in a century long war with a World Eaters force.
Since Arzach is the leader of this force I wanted his power armor to stick out from the rest of the marines. I figured he'd have an older looking suit (similar to an atificer suit). One way I tried to give the sense of age was to add a lot of rivets to the armor (a nod to the older Rogue Trader kits)... 68, I think.
I also built up the collar, reminiscent of the Inquisitor character, Tyrus the Witch-Hunter.
Here is a WIP pic of the model, just a few steps before I was ready to prime it.