Cranium design
- You may be looking for Cranium bulge.
Lacking the side handles of his Cyberman drones, the Telosian Cyber-Controller possessed a "special cranium design" which gave him his enhanced intelligence. (PROSE: The Powers Behind the Throne, TV: The Tomb of the Cybermen) He retained his enlarged cranium even after his Cyber-body was modified to the Neomorph form. (TV: Attack of the Cybermen, AUDIO: The Ultimate Cybermen)
A far future Cyber-Controller was similarily distinguished by a larger cranium with no side handles. (COMIC: The Flood)
A Cyber-Controller leading the weapons-grade Cybermen at the end of the universe also lacked side handles. Atop their cranium, which was not exceptionally large, was transparent glass through which their brain was visible. (COMIC: Supremacy of the Cybermen)
