Ghal Maraz, the "Skull Splitter," is the divine warhammer of Sigmar that dates from the mythic ages that predate the birth of the Mortal Realms. It is a great weapon of war and trails a twin-tailed comet when swung with sufficient force.
Grungni himself mined the starmetal of which Ghal Maraz was forged. Struck with runes of justice, the warhammer is a bane to Chaos and all its servants, and only the most powerful of the Dark Gods' minions can bear to look upon its radiant nimbus.
As legends from the mythic ages tell, Sigmar first used his warhammer to raise Mankind from barbaric squalor in the World That Was, wielding its might to unite a kingdom in the World That Was. Foes untold have fallen beneath its mauling blows, and while wielding Ghal Maraz Sigmar was never bested in combat.
Yet during the Battle of Burning Skies illusionary magics -- and his own impetuous rage -- tricked Sigmar into hurling Ghal Maraz into the void, where it was lost for many centuries.
Now, at last, the warhammer has been returned to Sigmar, who in turn has passed it on to his greatest champion.
- Order Battletome: Stormcast Eternals (1st Edition)