The Infernal Devices and the Mortal Instruments series are by Cassandra Clare. Both book series follow the Shadow Hunters, or Nephilim. The Mortal Instruments is the first series which takes place in modern day New York. The Infenal Devices is a prequel series and takes place in 19th century London. Both book series mention Marks/Runes which enable the ShadowHunters to heal themselves/ fight better/ not be visible to demons. The Shadowhunters mantain peace in the Shadow Relam/World. They hunt down demons and rouge Vampires, Werewolves, Warlocks and Faries (Never has happened but could).