Za Misuta
1
This takes place around 7 years before Naruto is born and a few years before war breaks out between the Shinobi villages.
Sandaime Kasekage received word on a strange yet important omen; a silver crowned black eagle with a white chest and glowing red eyes came to the where the messenger birds come at the hidden sand village. What coincidence was this an unknown bird with a scroll written in an unknown language- where did this bird come from and what was in the message? Those posted there were unable to catch this eagle but had obtained the scroll. The decoders were called immediately and attempted to translate what the message was about and try to trace its source.
It took about a month to translate the scroll which was enchanted by an unusual energy force. The translated text still didn't make much sense, all that it contained is the commentary of how an empire rose and fell, the title was "Kurevikku Kousen" . The story was out of order, yet they figured it out when they gained a better understanding of the material-that what was intended by the author. It did this to better tell the story of the protagonist, Za Misuta the founding emperor and how he eventually became a sage after death. What caught the Kage's attention is the character's immense powers, he could control the weather, bend the earth and wind to his will, master of the fire element, a magnificent general and political genius.
What the decoders figured out is the omen represented the reincarnation or rebirth of the Za Misuta, yet did not give specific details. So the Kage ordered the best summoning Shinobi to use advanced summoning jutsus to attempt to summon the spirit embedded to the paper. The first thing they uncovered was a graphic version of the story that appeared in a transparent form. The second attempt was the sage himself speaking in a language different to that of the scroll, his voice was recorded but the summoning could not be replicated. The Kage could not let this remain a mystery so they put a tremendous amount of effort to uncover the truth.
They ended up lucky; apparently a temporary shrine/portal would appear in the middle of the desert which according to the information understood the portal would disappear in 3 days. Immediately the Kage joined a team of 10 of his personal elite Shinobi; found the portal to the shrine of Za Misuta the sage of Time and Space.
They had to follow instructions on a summoning technique that had never been done before. After passing through all the barriers/illusions of the Temple they reached a marble pedestal where a silver baby sculpture with the clavic star inscribed on his right arm/shoulder and the eagle with wings spread on left, this baby is held out by the arms of the sage. The team leader performed the technique, an immense light and sound fills the room deafening and blinding everyone there for about 15 seconds.
When everything toned down all they could begin to hear is a baby crying - the ninja who did the summoning jutsu was nowhere to be seen. An elite recovered the baby and to their dismay the missing shinobi turned to silver in the place where the sage was standing holding out his arms to the altar. The Kazekage gave him the name Kurevikku Sejju (meaning Clavic Sage) since he is the reincarnation of the Za Misuta of the Clavic Empire, His aspiration is for him to be trained as a shinobi to become a dangerous weapon for the Village hidden in the Sand.
His history and origin was hidden from him and everyone else, it could be possible that other villages might have heard of this omen as well.