“From the maelstrom of a sundered world, the Eight Realms were born. The formless and the divine exploded into life. Strange, new worlds appeared in the firmament, each one gilded with spirits, gods and men. Noblest of the gods was Sigmar. For years beyond reckoning he illuminated the realms, wreathed in light and majesty as he carved out his reign. His strength was the power of thunder. His wisdom was infinite. Mortal and immortal alike kneeled before his lofty throne. Great empires rose and, for a while, treachery was banished. Sigmar claimed the land and sky as his own and ruled over a glorious age of myth.
But cruelty is tenacious. As had been forseen, the great alliance of gods and men tore itself apart. Myth and legend crumbled into Chaos. Darkness flooded the realms. Torture, slavery and fear replaced the glory that came before. Sigmar turned his back on the mortal kingdoms, disgusted by their fate. He fixed his gaze instead on the remains of the world he had lost long ago, brooding over its charred core, searching endlessly for a sign of hope. And then, in the dark heat of his rage, he caught a glimpse of something magnificent. He pictured a weapon born of the heavens. A beacon powerful enough to pierce the endless night. An army hewn from everything he had lost. Sigmar set his artisans to work and for long ages they toiled, striving to harness the power of the stars. As Sigmar’s great work neared completion, he turned back to the realms and saw that the dominion of Chaos was almost complete. The hour for vengeance had come. Finally, with lightning blazing across his brow, he stepped forth to unleash his creation.
The Age of Sigmar had begun.”
Warhammer Age of Sigmar: Generals Handbook