Historical Vampires

The vampire invaded Western Europe across the flat Hungarian plains as the Ottoman Turks retreated from the Slavic lands.  At first the vampire was a Christian -- a heretic or criminal or suicide -- whose restless soul would leave its grave at night, usually as a bat, to drink human blood but you could drive him off with a crucifix or garlic if you knew what you were doing.  In another form he was the incubus and the succubus having sex with people when they were sleeping.  As Christianity waned throughout the 19th century, the vampire began to wander the earth freely and without guilt -- and he could live forever.