Trench Crusade is a dark fantasy/alternate history setting where the First Crusade's capture of Jerusalem in 1099 led to the Knights Templar opening a gate to Hell, plunging the world into an eternal, technologically advanced World War I-era conflict. The forces of Heaven (Faithful) battle the Legions of Hell (Heretics) in a stalemate fought with demonic weaponry, miracles, and massive armor.
