The Cephalyx Dominator is a Unit Attachment model. His ability allows him to "recruit" any small or med base Merc unit to the Cephalyx. You get all the benefits of the unit plus they all become Cephalyx models. The Dominator acts like a lot of the other "hive-minds," in that it can sacrifice models in it's unit to ranged attacks against it and that the unit takes a big hit when he dies.
Once I knew I liked the color scheme, I had fun with getting into the lore and fluff. The Cephalyx are a hive structure army with tiers of "hive-minds" controlling thier respective tiers of "mind-slaves." Exulon Thexus, as the master "hive-mind," controls the mindless, beefy Monstrosities to lead the army as a battle group. As for the infantry, they are controlled by various lesser "hive-minds" called Dominators, Mind Slavers and Mind Benders. I don't have the Mind Slaver unit yet.
The lore behind the Cephalyx, is that the Exulon's surgically modify themselves with their most powerful enhancements and give the less powerful enhancements to these lesser "hive-minds." I chose to play the same idea into my color selection for these models. My armies main colors are going to be the Coal Black you see on Thexus's body and the purple of his robes. I chose to make the Coal Black my main for the majority of my unit leaders, with accents of purple draping and dark brown leather trim.
Drudges - The Fists and Punching Bags
The Drudges are the fists of the Cephalyx army. Numerous, expendable and pretty underwhelming by themselves. They become pretty beefy, pretty quickly, when you start to combo up buffs and use them to extend range of the Mind Bender's magic attacks. With the cheap cost of the unit, they definitely pull their wight in points.