The Toa of Miko-Koro is, ironically, name Light. His city is the city of mini Matoran [link]
Many Matoran of the other villages refer to them as the Mini Co-Korons as the Miko Matoran are made up of a variety of elements. Toa Light's power culminates in his clawed hands as before he became a Toa of Light he was an Earth Matoran, seen in his great arm strength and short height.
Light is the only Toa of Miko-Koro and his tale is a sad one. The Miko used to all be mask wearers as typical Matoran are, until the day everything changed. The city was assaulted by an army of Bohrok. Light was able to defeat them with the help of his trained Matoran warriors, which included Little Dude and his friends, along with the Miko Turaga. The village was saved but many of the defenders died, along with their Turaga. Having no other guidance, the Matoran looked to the Toa who had saved them. He sent the Matoran defenders back to their village to wait for his return as he would vanquish the Bohrok hive. Little Dude was reluncant to do so, wishing to follow the Toa into battle to fully defeat the Bohrok; he nonetheless complied.
The Toa of Light bravely headed in the direction the Bohrok had come, running into Bohrok here and there along his path. Eventually, he found a cave entrance, guarded by a small force of Bohrok. He defeated them and entered the cave, unbeknownst to him that Little Dude and his friends had followed in secret. They decided they would wait outside the cave for his return. Inside, Light snuck through the caverns, destroying Bohrok here and there, avoiding alerting them to his presence. It seemed like days before he was finally able to find the swarm hive.
Unfortunately, before he could destroy the hive with one strike of his light power, the Bohrok swarm was unleashed to commence a renewed attack on Miko-Koro, per orders of Icer [link]
. His attack did destroy the hive, preventing the creation of more Bohrok as well as destroying a third of those released. A long battle ensued, in the end Light was victorious. At a cost. His mask of life was shattered in the battle and left him weak along with other injuries. Bohrok he had not killed on his way in swarmed upon him.
Little Dude, awaiting outside had gotten bored and tired of watching Onions munch on onions. When he saw Bohrok returning and heading into the cave and the long length of time in which his Toa had not returned. He led his friends inside, following the last batch of Bohrok. They led him straight to Light and again found themselves impressed as Light decimated Bohrok after Bohrok until none remained along with the destruction of their hive. Hiding in the shadows, they did not see his injuries, but they noticed something about Light was different. He bore a krana of his slain enemies.
When the Bohrok had swarmed Light, he had been unprepared for when, suddenly, a leadership of the swarm krana landed upon his face. It attempted to corrupt him and the Bohrok watched, waiting for Light to become one of the swarm. Light avoided this fate by using his light powers to purge the krana, taking control of it. The Bohrok did not expect this and Light used his light elemental power to destroy them. He then slowly made his way back through the caverns the way he had come.
Little Dude and his friends watched as Light left. When he was gone, they excitedly popped out of their hiding spot and went in search of krana of their own. They found many, abandoning their masks and doning the krana they became corrupted. When Icer heard from his Bohrok swarm leader that the hive there had been destroyed he was dismayed at the failure, that was, until he was informed of the Matoran who had willingly taken up the krana. He had the Bohrok send commands to take all the krana they could find (still a task Little Dude and friends perform for no understood reason) and spread them among the Miko Matoran for the same reasons they had chosen them. They complied.
By the time Light made it back, it was too late. He found his entire village in an uproar, every Matoran wearing a krana, and Matoran from other villages either slain, wearing krana or running for their lives. In an attempt to quickly gain control over the situation, Light attempted to control them with his leadership of the swarm krana. The Bohrok at the other end sensed this and fought back for control. A battle of wills, Light won in the end, but the toll was atrocious, the sanity of every Matoran lost with a love for krana.
Light, suffering from his wounds, was now burdened with great dispair and he succumbed to his bodies demands, passing out. He was found days later by Toa that went to investigate the claims of the Matoran that fled. They healed him but found they could not remove the krana without killing him. They found no trace of his Matoran but did find the dead ones and the dead Bohrok swarm and destroyed hive. When Light awoke, they saw his great sorrow and found him to be without corruption and brought him back with them to Co-Koro to tell his tale. Light hopes one day to free his Matoran, believing that his only option is to use his light to banish the corruption from their krana.