The World of Warhammer is similar in size, layout and climate to the Earth, and spans several continents. It is orbited by two moons - the white moon Mannslieb and Morrslieb and the dark moon Mannslieb and Morrslieb. According to the earliest legends, the world was formed by a space faring race called the Old Ones, who possessed god-like powers. They built warp gates at the north and south poles which allowed them to travel quickly through space, but they were driven away from the planet when the warp gates collapsed, which initiated the coming of Chaos into the world.
The events leading to the Age of Reckoning start with a terrible Chaos plague which spreads through the Empire. Victims of the plague are transformed into Chaos-tainted mutants, and the population gradually descends into despair and panic. Emperor Emperor Karl Franz does what he can to stop the spread of the disease, but when the plague reaches the capital at Altdorf and unrest spreads across the realm he is forced to declare martial law to maintain the last remnants of normality.
Meanwhile, the Dwarf stronghold of Karak Eight Peaks is attacked by a massive Waaagh! jointly led by the Orc warboss Grumlok and the Goblin shaman Gazbag from the previously unknown Greenskin tribe called the Bloody Sun Boyz. The Dwarfs garrisoning the citadel grimly ready themselves for a long siege, but Gazbag directs a mighty blast of Waaagh! energy against the thick stone wall of the citadel, opening up a breach big enough for the greenskin horde to charge into the heart of the Dwarf stronghold. Karak Eight Peaks falls soon after.
The Dwarf High King, High King Thorgrim Grudgebearer, sends word to the Empire and vows vengeance against the ancient greenskin menace. Two months later, the gathered Dwarf host is interrupted as it is about to set out by an eerie eclipse. The skies darken as Morrslieb, the Chaos moon, slides across the face of the sun, bathing the land in a dull crimson glow. The eclipse is seen as a portent of doom, warning all those who see it of an impending catastrophe.
In the Empire, news reaches Karl Franz of a Chaos warhost led by a mighty Champion of Tzeentch marching from the north towards his borders. By now Imperial society has slipped even further into anarchy, and the Emperor realizes that his scattered forces are not strong enough to defeat the invading Chaos. With the Dwarfs occupied with the liberation of Karak Eight Peaks, he concludes that the only hope of saving the Empire lies with the High Elves.
Phoenix King Finubar, Phoenix King of Ulthuan, is already aware of the situation, and when the plea for aid arrives from the Empire, he gathers a fleet of elven warships and sets out personally with hundreds of the finest High Elf warriors, leaving Prince Tyrion to defend Ulthuan in his absence. The High Elves know that without the Empire to hold fast against marauding invasions from the Realm of Chaos, the entire Old World could be lost to the forces of the Chaos gods.
This is the moment Malekith, leader of the Dark Elves has been waiting for. Having been told of the gathering Chaos warhost by his most trusted seers, he conceived a plan whereby Ulthuan would be left vulnerable and open for an invasion, allowing Malekith to capture the throne of the Phoenix Kings for himself. Knowing that the Dwarfs needed to be distracted enough not to send aid to the Empire when the Chaos army invaded in order for the High Elves to be drawn into the conflict, he created magical amulets for Grumlok and Gazbag which greatly amplified their powers and compelled them towards Karak Eight Peaks, knowing that a Waaagh! would form around them as they traveled across the Badlands.
Now Malekith's scheme has come to fruition, and he launches his carefully prepared invasion fleet. The Black Arks of the Dark Elves set out from Naggaroth under cover of night to cross the sea to Ulthuan. One half of the fleet sails towards The Blighted Isle, while one half bears south towards the Straights of Lothern. Legions of black clad Druchii spill forth onto the shores of their ancestral homeland, armed to the teeth and accompanied by monstrous creatures.
The sheer scale of the threat arrayed against them from the combined forces of the Dark Elf, Chaos and Greenskin armies forces the leaders of the High Elves, Dwarfs and the Empire to gather at a summit in Altdorf. They pledge to put aside their differences to stand united against the tide of darkness which has risen against them all, to forge an Alliance of Order to strike back against their common enemies who would wipe civilization from the face of the earth.
Now is the time to take a stand. The Age of Reckoning is upon us.
The Winds of Magic, called the Aethyr in Elvish, is the name given by magic users for the invisible currents of magical energy which flow across the world. The source of all the Winds of Magic is the Realm of Chaos, and just as the emblem of Chaos has eight arrows, so does magic have eight winds.
When raw chaotic magic enters the world and encounters physical material, it is refracted into the eight 'colors', each of which can be used to create spells which are characteristic of the elemental nature of the magic being used. Human wizards generally only have an affinity with a single color of magic, while Elf magic users are more proficient and are able to use the full spectrum. Since all sources of magic involve playing with the essence of Chaos itself, all magic use carries with it an inherent risk.