Some design work for one of the current enemies opposing my players in Only War - the arch-militant (and heretek - which is sort of like calling yourself an engineer without having a degree, but more grimdark) Jarrian Holt, leading a force of the tech-thralls that are used by his lord-captain to maintain order (and repel the occasional assault by the Imperial Navy) aboard their void-ship. I'm still working on the full extent of his backstory, but I'm starting to get a Darth Vader vibe from him - "he's more machine now than man. Twisted and evil." Although I'm not even sure about how evil he is, now that I think about it.
Either way, his design has come together, at least.