Ten thousand years ago, Attai Horse-Speaker ruled a clan of Kellid barbarians in Nidal. This great horselord as well as his family were killed by a plague that swept through his clan. His followers honored their leader by building an impressive mausoleum that would stand the test of time. The Attai's mausoleum was revered for centuries but, eventually, his clan no longer returned to this sacred place.
A few decades ago, the relentless pressure from an aquifer connected to the Usk River caused some rooms within the cairn to collapse into watery sinkholes. In 4715 AR, a nereid named Maddy Whorlwalker and her nuckelavee companion, Kahak, invaded the tomb. Maddy was also accompanied by a number of loyal kelpies. The invasion awoke Attai's spirit as a rage-filled cairn wight.
Maddy and Kahak prowl the nearby Usk River every night, murdering travelers.