Great Colassian Desert
The dark elves and the humans are bitter enemies, but one thing that has slowed their war down is the Colassian Desert between them (also a tall mountain range). Apart from a small band of very fertile land alongside some rivers that cut across the desert. In addition to the normal dangers of deserts, the Colassian Desert has a lot of dangerous monsters and nomadic bands of gnolls which are equally hostile to humans and elves. The deserts are broken up by a few rivers with very thin bands of fertile flood plain and there is a band of savannah creating a buffer zone between the fertile southern lands and the arid desert. The Mereshnari clans are capable of surviving the desert well enough but most of them spend spend most of their time roaming the savannah.