Timeline
Age of The Gods
The Age of The Gods was the time when the gods lived on the world alone. Before even the Under Gods were borne. They lived in peace for millennia, as three families. However, after some time, the Old Gods decided to leave. Their sudden disappearance caused the three families to grow antagonistic of one another.
The three different families began to war against one another in the War of The Gods. The eldest members of the families, the Young Gods, met in secret and negotiated a peace. Their children, however, did not wish to abide by this new accord and chose to keep fighting. The Young Gods, seeing this, created hoards of monsters, demons and other creatures and unleashed them upon the world, driving back their own children. And thus began Age of Beasts.
War of The Gods
The War of The Gods began shortly after the Old Gods left the world. The three families were unable to reach an equilibrium of power once the Old Gods had gone.
The Young Gods met in secret to come to a peace agreement. However, their children refused to abide by the accord which was struck, so the Young Gods unleashed hoards of beasts upon the world in order to drive their own children back. At the same time, their created the Eldarani and Dendregaar to keep those beasts in check.
Age of Beasts
The Age of Beasts was borne out of the war of the gods. The Eldarani and Dendregaar were created shortly after the beasts and were made custodians of the planet, keeping the beasts in check. The Under Gods spread quickly across the world and tamed the beasts. The beast they could not tame, they built prisons for and locked them away. Ending the age, the greatest of all the beasts, The Great Beast, broke free, unleashing its minions upon the world, attacking the Under Gods. In order to re-imprison the beast, the Dendregaar bound the blood of their species to the land in order to strengthen the chains which bind it. This scorched the continent, making it nearly inhospitable.
At the end of the age, the Young Gods experimented with creating new beasts, and the result of their experiments was the mortals. These new creatures, however, were feeble and easily succumbed to the even the weakest of the beasts. In order to protect them, then Under Gods, along with the greatest of the mortals, destroyed the great beasts. The few that remain are those that live, domesticated by the Under Gods. Possibly, the greatest ones, which were in prison, are also still around and have been long since forgotten by the mortals.
Age of Mortals
After the world was purged of beasts, the mortals quickly spread across the continents. The Eldarani retreated to Matrellis. The Dendregaar remained in isolation on The Desolate Continent. Mortals quickly built their own nations, and, over the generations, forgot their origins, and Age of Beasts. Those beasts became nothing more than myths and legends; many mortals don't even believe that the beasts were ever anything more.