The Wiglaff Tales. The Wiglaff Chronicles, #1

Roman imperial forces are massing to invade and enslave Caledonia. Wiglaff, son of the great warrior Mordru, is shunned by his father as unsuitable warrior material.  An unusual child, Wiglaff has visions and an uncanny relationship with the natural world. He becomes the  protégé of the shaman Ugard and learns how to focus his powers to bring rain and affect events. Meanwhile, Wiglaff's warrior sister Winna, quietly forms a band of warrior women from the nearby villages.  The shaman, his protégé Wiglaff, and Winna join forces to combat this formidable enemy.  Imperial forces mass for an onslaught against the villagers, and the situation looks hopeless until the shamans defeat the enemy by using white and black magic.  Alma, a Roman double agent, insinuates herself into Wiglaff's household and provides critical intelligence about imperial intentions and movements. Wiglaff foresees a greater threat to Caledonia than imperial forces however, as two Roman scouts are taken prisoner by Winna's warriors who are followers of a crucified man named Jesus.
When negotiations break down and the Caledonian Confederacy prepares to go to all-out war with Rome, will Wiglaff and his companions be able to save their village?