Balance in the sword is balance in the spirit.
The Iron Clan is home to a martial branch of Shadow Warriors known as the Ohan. Though they seem to rely solely on martial skills the connection the Ohan have with their Koto swords transcends the physical.
Though the forging of the Koto blade is secret to the Iron Clan the thin blade wielded by the Ohan are believed to be fused with elemental energies. To harness the power of the koto one must be balanced in self or wielded themselves.
As tension between the Higurian clans of Spirit and Iron they built a wall to seperate the east and west of Higura. And though the Iron Clan keep close behind the wall they built the rivalry between the clans remains.