As the Ice Age was ending, melting glaciers caused the Old Water to rise, surmounting the tops of the Quaxo Hills and spreading westward. The Hollow Lands were inundated by the New Water. Many sentient beings, Liskash and Mrem alike, were killed in the flood, while those insightful enough to see the signs were able to get out beforehand. On the south side of the New Water, the Warm Lands were dominated by Liskash. Mrem who lived there were slaves to Liskash, or lived in nomadic groups by vigilantly defying the "dinos."
The fictional geography appears to be based on a mirror image of the Mediterranean basin, with the path to the ocean in the east, rather than the west as in our world. The Old Water is analogous to the Atlantic Ocean, the Quaxo Hills represent the Straits of Gibraltar, the New Water resembles the Mediterranean Sea, and the Warm Lands appear to be North Africa.
The Hollow Lands and the New Water were known in some subcultures as the Hot Depths and the New Sea. According to "Battle's Tide" by Michael Z. Williamson, the third story in Exiled: Clan of the Claw.