The planet of Laia has existed for billions of years - for time so long that there are very, very few gods that exist that even know the oldest legends of the beginning of its creation. It is thought that life has cycled through flourishing and death on the planet at least a few times before, building up into fantastic civilizations that were somehow utterly and completely destroyed. Rumors exist of ancient ages of giants whose bones make some of the mountains and canyons of today, of an age of endless water, and of a darker age of ancient darkness.
The current age has stretched on for hundreds of thousands of years, giving rise to a lush diversity of life on the planet as life reclaimed the ancient rock. Gods and demons, mortals and plants, creatures of all manner and nature thrived together in a rich and vibrant world, competing and working with one another as civilization rose up from the shadows and great nations and peoples became established.
Certain creatures developed that harnessed the elemental life-forces of the planet better than others - and many of these creatures, in time, became gods; creatures who were born of the holy or dark energy that saturated the world, many of which also had ties to more base elements such as earth, water, air, and fire. Other creatures developed no such specialization to the energies of the planet, but the ability to wield or endure all the elemental energies - such as the vast majority of the mortal races, who often found themselves under the protection of or exploited by the tremendously powerful gods.
At times the gods fought among one another, destroying land and entire peoples along with one another, or exploited the mortals until they were able to rise above their weaknesses and overcome the gods. Wars between the gods and mortals, between god and god, and between mortal and mortal were not uncommon... yet, somehow, balance always seemed to find a way.
Until the Abyss Wars.
~1,000 years ago -> The Abyss Wars begin, starting small and quickly growing to cover entire continents and sections of the world. The most powerful gods are on various sides, Dark and Holy mixing with one another as they formed alliances to support their desires.
~700 years ago -> Abyss War ends, the Goddess Avavel dies and, with her dying breath, she casts the Abyss spell that causes the Holy and Dark gods to be torn from the world into their own realms. The world becomes a shattered layer of dimensions - the Holy, Dark, and mortal realms. A jagged scar that circles the world (so it is thought) appears in the ground, a canyon filled with dark light that stretches as far as the eye can see down into the depths of the earth and up into the stars of the sky. No one can get through the spell - all who enter disappear.
At the sight of her death and the assumed loss of the war, hundreds of the mages in Avavel sacrifice their lives or powers in an equally powerful spell to hide the city of Avavel and prevent the enemy forces from accessing its tremendous knowledge and powerful - unknown to them, most of the enemy forces disappeared with the creation of the Abyss spell.
With the world torn apart by war, some of the most powerful magical cities destroyed or hidden like Avavel, and the gods that have existed for eons alongside mortals disappearing... much of the world falls backwards in time, civilizations becoming extremely independent and cultures having to reestablish and recreate themselves. Travel between lands, once so involved that someone could travel the entire world, practically ceases beyond some trade. Countless lives have been lost - nearly all the world's population from the war - and with populations so scarce there is even less incentive to travel. From the loss of knowledge many technologies and magical abilities - once at their prime - have been lost completely.
After the war the people who had been pushed to the land of Avavel, one of the last remaining powerful gods who fought to protect the mortals, dispersed. Many refused to stay so close to where Avavel had been killed and where the Abyss was, but a few settled close by.
~30 years ago-> The Abyss spells begin weakening, though no one is sure at first. The veil cackles with lightning and various places in the world begin to experience tremendous earthquakes.
Year 0 -> Avavel Rediscovered as the spell hiding it finally wears off, occurred 2 years ago and was such a huge, tremendous event that it reset calendars as far as many villages were concerned. With the extensive wealth of information from the most developed times suddenly available again, technology and magical understanding are primed to leap forward hundreds of years ahead of the rate they had been re-progressing on.