Hyōkaidō (氷塊洞, Literally meaning: Ice Block Cave) is one of the big six unexplored sage regions, a legendary place that is equally famous as the others, Black Dragon Cove, Majonomori Forest, Island of Bakeneko Tribe, Bewitching Silk Forest and Silk Forest of Submission. It is the residence of the arctic foxes — including the sacred Nine-Tailed Sage that resides in the cave and currently rules the entirety of the Fox — and is also where Yaban trained here to achieve Sage Mode. Unlike the other sages, the foxes of Hyoukai Cave seem to have more affiliations across the globe showing they are a universal species, despite at least four of their summoners originating from the Yukishiogakure. Also, three of their foxes seemed to show great intelligence that earned them a seat in the Village Council.
the way and distance to Hyōkaidō would take a few hours from Fuyugakure to reach it, six days from Land of Kaiju, seven days from Bewitching Silk Forest and a month from Land of Owls despite Land of Fruit only being two or three hours from the country. In their experience, only those with sheer determination and an iron will can come to Hyōukai Cave. In order to be granted audience to learn senjutsu with the fox sage, one must pass three trials posed by the foxes. According to the rules, if a candidate fails at any of the trials, the foxes are allowed to kill or keep them as their slave or sex slave. One section of the cave is made of dolomite, the surface is mostly covered by the castle it is also seen covered with gems of different varieties, the Sage's chamber or Fox Nest is littered with Gypsum and Rubies, its territories also include fenlands.