The Toa Guardians
In times ancient, Mata Nui decided to create a new breed of Toa: The Guardians.
The Toa Guardians were ancient Toa teams who have gone through a protodermis bath together. The resulting merged form has control over every element. They are almighty beings, kept secret to all but the highest in the Order and the Great Spirit himself.
They are the scouts and researchers of Mata Nui, stationed on the planets he visits, monitoring the life there, transmitting the data to Mata Nui, in hopes that the War which tore Sphereus Magna apart would not be repeated.
They are unparalleled in skill, unmatched in strength and unrivaled in ferocity. The greatest among them has faced an entire tribe of Skakdi on their own island. When he left, there was no tribe to speak of. One of the least among them went by the name of Lesovikk, who, though unknowing of his origins and stripped of rank and power, is legendary nonetheless.
They always go through a special mutation to better blend in with their planet's dominant species. Such disguises are meant to help maintain radar silence, but are not foolproof. Many races thus have developed the legend of the cyborg.
Through war, they broker peace, through peace, they prepare for war. Such is the way of the Guardian Toa.