The Three Brothers were the three major mines in the remote plateau known as the Lair, the last stronghold of the Boar Clan. Iron, copper and jade veins were found there. They were named after three brothers of the original scouting party led by Heichi Jomei that discovered the Lair, Heichi Goshoryu, Heichi Dammaku, and Heichi Ozashin. The largest mine, rich in iron, was named after Goshoryu. Ozashin's name passed to the valley's small jade mine, and a tunnel named Ozashin's Relief was an emergency escape route for Heichi sano Negura, the castle being constructed by Heichi Jomei. The third mine with extensive deposits of both iron and copper, as well as occasional small veins of gold, was named after Ozashin.