The Unbroken was a secret otokodate of Tainted ronin. It was created in the 12th century by a small group of ronin and the Ashlim, a powerful Naga Jakla. They are the sworn enemies of the Shadowlands, and by fighting the creature they can cleanse themselves of the taint. 
Before the Clan Wars, a band of thirty ronin ventured into the Shadowlands in hopes of defeating a monster and gaining fealty of the Crab Clan during a Twenty Goblin Winter.  However, they were unprepared for the danger and many were killed and the dozen left over were all tainted. The now smaller group fled past the Kaiu Kabe into the Shinomen Mori.
In the forest, the ronin were discovered by a group of recently awakened Naga, lead by the Ashlim, a Jakla. The Naga quickly captured the ronin. Even though they were tainted, Ashlim saw how the ronin worked for each other as a single mind and was reminded of the Akasha. He entered a deal with the ronin, if they would help him study the taint, he would cure them of their corruption. At first many of the ronin’s taint grew out of control and they had to be killed. But, Ashlim then created a variant of the Naga immunization process against the Taint. The spell slowed the taint but greatly shortened the human’s life span to a single year. Ashlim refined the spell more and the cure the ronin were hoping for became a reality.
By turning their chi against the taint in meditation they could reverse the taint, but their time was limited. Instead, they personalized the battle of the taint by destroying the minions of the Shadowlands. If they could kill enough of the tainted spawn before their short time was up, they could be completely cured of the taint. With this hope, the Unbroken were formed. 
The Unbroken work as a single mind. Each ronin was willing to sacrifice themselves for another. Only a handful of the original ronin had become cured but they continued to fight alongside their comrades. The entire unit was small; to be sure there was enough time to redeem everyone. It had acquired new tainted ronin and some Naga warriors, but moved in secret. The entire unit was masked, to remind themselves there was no difference between the pure and the tainted in their ranks. They all must work together or they will all fall together. 
The band had formed and collapsed many times, re-organizing whenever a Tainted wave-man managed to unearth the secrets of its technique.