Matoran Civil War
Prior to the war, there were disputes that raised tensions between Ta-Matoran and Po-Matoran in Metru Nui which led to acts of vandalism.
In the wake of these events, they turned to their Turaga for negotiations, but she proved to be unable to stop the hostility, only leading them to more conflict.
Soon the outbreaks of violence began to branch out into the other Metru regions. Profits were lost in transit, then borders were crossed unlawfully. The violence escalated without pause until it finally reached across every shore.
In the end, Le and Ko-Matoran stood with Po-Metru while the Ga and Onu-Matoran stood with Ta-Metru. Both sides stood relentlessly against each other until the bitter and bloody end.
In the midst of the chaos, the Makuta Mutran, seeking "subjects" to test his Rahi against, released his newest creations on to the warring Matoran of Metru Nui, as the destruction caused by them would not be noticed among the mayhem left by the war.
He found out his Rahi beasts will make promising weapons for the Makuta in the near future.
By spreading false information to both sides, Makuta Teridax successfully lured the Matoran militas into the Archives. Inspired by Mutran's "experiments", Teridax released the archived Rahi to wipe out the warring armies...all of them.
The war has ended, at the cost of countless lives in the Archives Massacre and the reputation of the Makuta. With the disappearance of the war leaders, the time of peace has begun. The question is: for how long?