Kinda a general one,
Years and years ago there was a great village thriving, a village which took no part in the world of the Shinobi. These monks did have chakra, but they used their chakra to help them in life and to help others; never for fighting. During a Shinobi war this Village of Monks was targeted and taken out. The great monk of the village left one last prophecy before he died.
In 100 years the Moon will fall cold, Earthquakes will trigger eruptions and our small Village will finally be covered by great Tsunami's. When this occurs you will know the world is nearing its final days, and a great enemy will be born.
The prophecy was kept quiet. Now the Prophecy is only known to Kage's and their closest Shinobi/ advisers. The problem is though, the island where the Monks where rumoured to live has just been subjected to what was told in the prophecy and now the Kage's are worrying and preparing their Village for the worst. The village's plan to build up great armies of only elite shinobi to take on this great enemy, but none of the shinobi know of this yet.