Ghal-Maraz

The hammer that started it all.

Ghal-Maraz ("skull-splitter" in Dwarvish) is Sigmar's main weapon and according to some the "Warhammer" of the franchise. As such it bears special symbolism for all things Warhammer.

Warhammer Fantasy

It was originally a two-handed hammer forged by the dwarfs for the Dwarf king Kurgan Ironbeard, but the dorf gave it to Sigmar as a gift for saving his and his kindwarf's asses from a mob of Orks. It became the symbol of the Empire and the favorite weapon of the Emperors. It has some kind of magical power due to the Dwarven runes engraved on it, which helped out a lot at times. For instance, when Sigmar he fought the leader of the Middenland and the hammer was blessed by Ulric after said leader threw Sigmar into Ulric's flame, only for him to come back out completely unharmed and shatter the leader's precious long sword along with his skull. The other is during the last battle against Nagash, where the moment Sigmar is about to strike at Nagash with the hammer, it suddenly grows with Dwarven rune magic from its rune. Using that power, Sigmar hit the Nagash's bone rib. The bad chemistry of Dwarven magic mixed with Nagash's dark magic has created some form of instability within the bone daddy himself and was BLOWN. THE. FUCK. OUT. to the sky.

After Sigmar's absence, the hammer was passed down from Emperor to Emperor all the way to Karl Franz where he smashed many orks with the hammer, then to Valten after many people believe he was the reincarnation of Sigmar himself.

During The End Times, Valten carried the hammer to smash many a chaos prick (Notably: Crom the Conqueror, Wulfrik the Wanderer, Count Mordrek the Damned and a changeling that impersonate Gelt's disciple) while on his way to Middenland. He was ultimately killed by a backstabby Vermin Lord Deceiver after being exhausted from his duel with Archaon. The hammer was in Archaon's care for a while until Sigmar manage to reunited with his hammer then smash Ka'bandha's face with it. It allows him to outmatch Archaon in battle but it was not enough to save Mallus (the Warhammer world) with both Sigmar, Ghal-Maraz and Archaon falling through a warp-rift which consumed the planet.

Both Sigmar and Ghal-Maraz managed to survive the apocalypse and were merged with the essence of the Realm of Heavens, becoming even more powerful than ever, unfortunately Tzeentch tricked Sigmar into throwing Ghal-Maraz into another warp-rift while trying to strike down Archaon, which ensured Sigmar's withdrawal and the coming of the Age of Chaos.

Age of Sigmar

With the coming of the Age of Sigmar one of the first tasks the God-King gave to the Stormcast Eternals was to recover Ghal-Maraz, they succeeded and Sigmar gave the hammer to the Celestial-Prime (we still don't know his true identity but people think it is Settra the Imperishable, Alcadizaar, or Karl Franz). The Celestial-Prime, now named after the hammer, managed to rescue Alarielle the Everqueen of the Realm of Life from being caught by Nurgle while in the process defeating Chaos Lord Torglug the Despised, killing the chaos guy like the failure he is No wait! You thought it was slay-the-heretic-inquisition-time as usual? Ghal-Maraz is presently imbued with the power of Noblebright, and it purged Torglug, bringing him back as a Stormcast Eternal, that's right kids, Sigmar's main weapon can pull back mortals from corruption (as long as there is still some sliver of soul to be saved, so you better don't try this with Archaon), needless to said, Nurgle needed a lot of ice after that incident.

Tabletop

Ghal-Maraz was wielded by only two people on the tabletop prior to Age of Sigmar: Karl Franz and Valten. Both got the same use out of it: all hits automatically wound, allow no armor saves and deal d3 wounds. This means that you roll to hit, then roll 1d3 per hit to see how many wounds your opponent eats. Given that both karl Franz and Valten had pretty high WS and Attack stats, this means that in a duel they wreck face like it's nobody's business and could deal massive damage against infantry hordes, especially when paired with either a monstrous mount (like Karl Franz), a large support unit (Valten) or even both if you can afford it.