Until the Great Schism in the 14th century, Earth's history was the same as we know it now, except magic-using wizards often manipulated important events. Sometimes these wizards influenced history secretly. Sometimes they made history openly. The most powerful wizards ascended to immortality and godhood. These wizards and gods are the source of many myths and legends.
THE GREAT SCHISM:
At the end of the 14th century, Earth shattered into innumerable fragments in a magic-instigated apocalypse called the Great Schism. Baldr and his adherents commonly use the term Ragnarok to refer to the conflicts and cataclysms which resulted in the Great Schism. Powerful magic allows fragments of Earth to endure as habitable, island realms scattered between planes of existence.
LIMBO & THE REALMS OF CHAOS:
With Earth destroyed, wizards and their gods made a new home on a magical planet called Limbo. From Limbo, these wizards and gods engage in eternal conflict over who controls the many, surviving realms of old Earth. Each realm holds the promise of ancient artifacts, lore, and power to fuel the ambitions of wizards and gods alike. It is a feudal, dystopic society of magic users.
Science fiction and fantasy author Allen Stroud is writing a novel, The Death of Gods, which will tell tales of the secret history leading up the destruction of Earth. You can read up on his Chaos Reborn world development in his blog. Other official stories can be found at the official Chaos Reborn fiction webpage.