Sigmar Heldenhammer is the founder, first Emperor, and — in time — the god of the Empire of Man. His legend begins with a twin-tailed comet blazing across the heavens on the night of his birth, and every part of it thereafter is just as outsized. As a young chieftain's son of the Unberogen tribe, he rescued the dwarf High King Kurgan Ironbeard from orc captors, earning as his reward the runic warhammer Ghal Maraz, the Skull-Splitter, and a friendship with the Dwarfen Mountain Holds that endures twenty-five centuries later.
Sigmar spent his life hammering the feuding human tribes into one nation, and sealed the work in blood at Black Fire Pass, where men and dwarfs together annihilated the greatest orc invasion of the age. Crowned Emperor, he reigned for fifty years — then laid down the crown and walked east into the mountains, alone, and was never seen again.
His people concluded he had ascended to godhood. The Cult of Sigmar became the Empire's spine: its Grand Theogonist crowns emperors, its warrior priests march with every army, and Ghal Maraz passes from ruler to ruler as the badge of his legacy. In the Empire's darkest hour it was a priest of Sigmar, Magnus the Pious, who invoked that legacy to win the Great War Against Chaos. Whether Sigmar truly ascended, or merely died in the eastern peaks, is a question his church does not encourage.