The Dene (Athabaskan) peoples of the region — particularly the Nahanni Dene or Naha tribe — have oral traditions describing the Nahanni River valley as a place of spiritual power and danger. The Naha themselves are a semi-legendary people who lived in the upper reaches of the valley and were said to be fierce warriors who vanished mysteriously. Some Dene traditions describe them as a people who retreated deeper and deeper into the mountains until they disappeared entirely, leaving behind only campfire rings and stories.

The valley's reputation intensified in the early 20th century when prospectors began entering the region during gold rushes. In 1908, the McLeod brothers were found dead in the valley — according to most accounts, decapitated, though the details vary with the telling. Over the following decades, other prospectors disappeared or were found dead under mysterious circumstances. The valley acquired the name 'Headless Valley' and became a staple of Canadian frontier mythology.

The convergence of ancient Dene traditions about a vanished warrior people and modern disappearances created a layered mythology — Indigenous cosmology meeting frontier horror story. The Naha remain one of Canada's most compelling ethnographic mysteries: were they a real band who migrated elsewhere, a metaphorical representation of wilderness danger, or something else entirely?