Bury Me with My Weapon:

In a land of magic on the knife's edge of perpetual ruin by a centuries old war, Mastiff of the Dog Parable, Shade an assassin of the Order of the Branch and Ghost a scholar of magic in the College of the Unturned Stone, are sent to test the validity of a foreign prince's claim to a mysterious power used to keep the ruling authorities in the war from going too far. What they find instead will force them closer together and further from the houses they knew.