Grendlr conversion some time back. The Cthonian looks nice as a robot, but never really spoke to me as a giant evil pseudo-organic intelligence, which demanded a change.
The first step was a widened posture, a trick I first tried with the Avatar of Menoth to bulk out a similarly small model. He got a bunch of tubing, and a more organic carapace and weapon. Finally, he got some creepy infestation base work done (complete with a Samaritan being "processed").
So, my regular, old Cthonian will be doing duty as the Assault Drone variant, while this big guy will be my main evil AI.