The Skullhelm gives Tretch a 4+ ward save and the ability, once per game, to re-roll a dice roll. The re-roll can be one of his To Hit, To Wound, armour or ward save rolls, or a Leadership test for his Stay Here, I'll Get Help! special rule.
Source: Warhammer Fantasy: 8th Edition
The Skullhelm gives Tretch a 4+ ward save and the ability, once per game, to re-roll a dice roll. The re-roll can be one of his To Hit, To Wound, armour or ward save rolls, or a Leadership test for his Stay Here, I'll Get Help! special rule.