Before the 1950s, Louis lived in Hungary. Over the span of his long years as a vampire, Louis lost a bit of sanity and had surrounded himself with death and sorrow for it. He steadily fed off of humans and had a particular liking for children, thinking their blood is the purest and sweetest, since young flesh is the tenderest. He apparently played with them awhile after they were dead. Eventually, Louis was chased out by the local mundanes who found his lair filled with children's corpses.
Louis escaped to New York and was promptly welcomed by Camille Belcourt, an old and powerful vampire and the head of the local clan. Unfortunately, he began to kidnap children again and caught the attention of both mundanes and Downworlders.
One evening in 1953, a gang of teenage boys hoping to rid their streets of vampires went to the Hotel Dumort to slay them. Among them was the young Raphael Santiago, whom Karnstein spared and even Turned, thinking he would help him with the others. Instead, Raphael destroyed him, presumably forcefully burned in the sunlight because, as Raphael later described his death, he soon turned to ashes and drifted off through the roof of the hotel.
- Saving Raphael Santiago (first and only appearance)