It is Remnants, the latest novel from amazing author Lisa T. Bergrem. (Pre-order before April 8—best prices! $11.95 hardcover, $7.99 Kindle)
Here's what it is about:"Our coming was foretold by the elders--- Those who would change the future, just as the planet teetered on the edge of darkness. Born on the prophesied day with birthmarks in the form of a crescent moon, they knew us immediately. Swaddled and screaming, we were spirited away by those who hid us, trained us, and kept us safe until our time came. They poured their lives into us. Some died to save us. And now we, the Remnants, protected by Knights of the Last Order, have gathered. Called until we breathe our last ... to save the world."
Read the first two chapters here.