The Witch and the Long Rifle
Mankind is on the brink of defeat. The Grand Theocracy of the Americas has declared total war on an invading alien race known as the Grimma, mobilizing the military branches of each of its provinces for the sole purpose of destroying them before they enslave all of humanity and sap them of the energy Einstein called Vitae Essentia.
Matt Falkirk is a Marine, a Combat Cleric of the Order of Knights Hospitaller tasked with healing his fellow Marines during battle and ensuring their wellness at all other times. He's ready to fight, kill, and die in order to protect his planet and his people from harm.
At least he was before he woke up in a cave with the worst headache of his life and his short term memory wiped clean.