30% of skull

Ghazghkull became a Goff with a mission after losing 30% of his skull to a Bolter shell coming the other way. While recovering from his wounds, Ghazghkull started to feel vague prickling sensations in the back of his head. He soon found that in the fury of combat he was filled with energy and power, which enabled him to crush all before him. [...] With the aid of his newly discovered psychic power he has impressed a large number of Goffs into joining him and now commands the loyalty of a large and well armed Warband.

- 'Ere We Go, page 153