Ghal Maraz
From Warhammer - The Old World - Lexicanum
The Hammer of Sigmar, Ghal Maraz, was wielded by the famed founder of the Empire Sigmar Heldenhammer and has been passed down from Emperor to Emperor. It is currently held by Karl Franz, who, during the Storm of Chaos granted it to Valten, Sigmar's apparent champion to wield. Upon Valten's death the hammer passed back to Karl Franz.