The time period known as Advent, also called the Time of Beginnings, is known as AV on the Anasatar World Calendar. Advent begins 20000 years after the Creation.
The gods watched over Anasatar peacefully for a time but soon fell into squabbling amongst themselves. While each god had their own function and domain, several gods believed that they could do better than their peers. Thus a great war erupted in the higher planes, one that would almost completely annihilate the original divine pantheon, requiring the direct intervention of Lord Ao himself.
Almost three-quarters of the original pantheon was slain, with most of those who had survived having taken no sides in the divine conflict. As the gods had been preoccupied with their war, they had neglected their primary duty, that of tending to life upon Anasatar. As such, the planet had withered and died, leaving it a near lifeless husk.
Lord Ao became enraged at the sight and immediately destroyed many of the survivors of the war, leaving only those who had attempted to faithfully carry out their duty (in vain) alive.
The gods who survived Lord Ao’s culling were given greater power to compensate for the loss of the pantheon and Lord Ao created a new pantheon of gods and goddesses by bringing in successful deities of other worlds.
With these new gods came many followers from other realms and soon Anasatar was teeming with life.
The new gods and goddesses had a distinct advantage over the native Anasatar pantheon in that they had many followers from which to draw power. After the Time of Beginnings, many of the old Anasatar Pantheon either “died” from lack of worshipers or were demoted to lesser roles within the new Pantheon.