The One-Tailed Beast is one of the Land of Mountains Biju. It is a giant long-necked beast that dwells in a deep lake in the northern parts of the land. It is a creature believed to inhabit, specifically, Lake Yama-Tora in the Land of Mountains' Highlands. It is similar to other supposed lake monsters in the area and elsewhere in the land, though its description varies from one account to the next. Popular interest and belief in the animal has fluctuated since it was brought to the world's attention in early days of Yamagakure 2.