The Rend

The Rend was the event that caused the split between The Arxi, causing the creation of the The Fulcra, and The Fallen.
The powers of The Ourvorax created what the Arxi perceived as prisons. These prisons were under the Mortal Realm Astrum and were the opposite of The Hallows Above. They would later be called The Circles Below. The Arxi began to accuse each other of being deserving to be caged, for The Ourvorax wouldn't have created prisons if one of The Arxi didn't deserved to be imprisoned, right? Well, thats what The Arxi thought.
Eventually two sides formed in this argument, and eventually one lost. Those that lost were banished to the cages, The Circles Below, never to be free. They were called The Fallen. Those that remained in The Hallows Above were namede the Fulcra.
Of course, since the Circles are below the Mortal Realm, the Fulcra had to send the Fallen through Altus, and it was a violent entrance and exit. The liberi, the first mortals, were wiped out, their population gone, because of the brutal powers of The Fallen as they were hurled through The Mortal Realm. The end of the liberi marked the end of the Earliest Era.
Though The Fallen are locked away in the Circles, there are still remnants of their power on Altis. The most prominent example of this is the existence of the inferis. Much like how the elves were born from the residuum of The Forgotten's power, the inferis rose from the ashes of the liberi and the scars that The Fallen has left.