After some serious detective work I managed to get my hands on some Rogue Trader Imperial robots for use with my adeptus mechanicus genestealer cult. The first off the assembly line is this venerable castellan. It's my favourite of the old robots, and was a real treat to paint. I've kept him in mechanicus colours, albeit somewhat tarnished and battle worn. I figure the cult isn't too big on keeping it's machines in parade condition when it's fighting for control of the cities.
Next up is a controller for this automaton. I think a heirarch with a control panel will do the job nicely.
Here he is with a large hybrid for a bit of scale. He's on a 40mm base, so small by today's standards, but meaty enough for my purposes. Another four of his brethren will be joining him in time.