Lord Castellan appers to be a one off type of character and probably wont make any appearances outside of flash backs. At first he seems to be evil in his goal to kill Skiki and his friends as well as any other humans  off planet however this is all just a ruse to get Shiki to leave the planet so he doesn't have to watch everyone shut down and die. 

I imagine him to have a lower and rough voice. There's no need to do a robotic tone as I will be adding an effect to the audio myself.