Before Nightfall Amet was home to the Arethian Empire and Universitas. The Nightfall ritual created a portal between Amet and Hell, turning everything but Universitas into a volcanic hellscape and the continent was taken over by legions of Areth's devils. During The Reckoning The Circle of Kiral, a human resistance army and the mages of Universitas fought the legions of Areth in order to distract the devils and close the Hell portal from their end. When the portal was closed and Hell was destroyed by the rebirth of Itoa thousands of devils were stranded on Amet. To stop the bloodshed the devils and the circle made a deal imprisoning the infernal legions on Amet.
Led by Ego Ultd. CEO Anders Hillstrider the mages of Universitas and the devils have together rehabilitated the lands between the university and the continents capital. Both the volcanic ground and the mingling between devils and mages proved quite fertile and in the centuries since The Reckoning the cities' population has expanded exponentially, eventually creating one single sprawling urban cityscape called New Amet with small frontier towns on the borders of the habitable zone where mostly slaves toil to transform more and more of the continent into fertile farmland to feed the ever increasing appetite of the city sprawl.
All but the most powerful devils from the infernal legions have since died either in power struggles with their neighbors or by the hand of Maevin's crusade, however their tiefling descendants are common as dirt and also treated as such.