The Naiyeni is one of the Myr's longest rivers, rivalled only by the Mymidon River in distant Helyas. The Naiyeni is deep river, fueled by the many streams running down from the Acoran Ranges in the north. The Naiyeni's source is in the Acoran foothills forty leagues north of the capital Efnissien.

The river is home to the deadly praga fish, a small, ugly and mean freshwater fish whose sharp teeth are only rivalled by its claws.

Naiyeni means 'whisper carrier'. Remarkably, the river carries sounds the way most water ways carry leaves. It is said that something spoken upon the river's edge in Efnissien could be heard the following day in Griflet 150 leagues away. This has enabled an extraordinary line of communication between Efnissien and Griflet. To this end, the late King of Acoran stationed 'whisper-gatherers' in Griflet, men and women who patrol the banks of the Naiyeni where it cuts through the centre of the portside town, listening for any word from the north. This job is paid handsomely; many Acoran whisper-gatherers has lost entire ears to the viscious praga fish, who will cunningly follow the ripples of a whisper all the way downstream just to feed of the flesh of a careless whisper-gatherer.