Lionheart: Legacy of the Crusader

Richard the Lionheart's massacre of 3000 prisoners at the Siege of Acre, during the Third Crusade, was used by a villainous character as fuel for a ritual which tore the fabric of reality. This resulted in magic invading the world from other mysterious dimensions. Our world has changed forever when it was ravaged by this uncontrolled magic and hordes of demonic creatures.