The Spear of Destiny by M E Brines : 2011

Goodreads.com Description The Spear of Destiny – 10,000 word supernatural alternate history novella -- Seeking bloodthirsty revenge for the death of his brother in World War II, young seminary student Stuart Mackenzie abandons his theological studies to become an agent behind the enemy lines where he discovers a diabolical Nazi scheme to employ black magic as a secret weapon on a vast scale powered by millions of human sacrifices. What chance will the mundane weapons of the Allied powers have against ancient magic and an artifact said to have slain the very Son of God?