Karl Marsten was the son of the late Josef Marsten.
He was born a Werewolf and brought up as a Mutt. He has followed in his father's footsteps and became a professional thief. He was dating Hope Adams, though he proposed to her in the short story "Lucifer's Daughter" and who he has one daughter Nita Marsten with, later a son. He is featured heavily in Personal Demon and Living With The Dead, notably nearly dying from a cult's invasion then temporarily possessed by his father-in-law in Thirteen. He taught Hope the basics of breaking and entering. He also recently joined the Pack, although not as a major member like Elena Michaels or Clayton Danvers, after Bitten, but becoming a father pushes him to change for his "new" family. He gives a charm, then engagement ring, to Hope inscribed with No matter what showing his devotion and love as a couple and mates.
Due to his career as a jewel thief, he is skilled in sleight-of-hand, various securities, several languages, monetary acumen, transportation and fashion sense. His fashion sense is emphasized by Hope to be the key that made her mother accept their marriage with several decades of difference and Hope's fashion "savior"/director in their growing family. As a previous long time bachelor, Karl also possess high skill in cooking, cleaning and domestic psychology.
As a couple, Karl is described as a James Bond with his Bollywood star, Hope.
He has self-esteem issues towards showing his scarred body to others, excluding Hope, who views them with pride. Karl also is perverted on a level between Elena-Clayton and Jaime-Jeremy, he does not seek sex for every emotional up-down or every time they meet up. Instead, Karl would even try "fun" when Hope is stably pregnant.
Otherworld Series Edit
He is part of the uprising and is the only one to survive. He helped Elena kill the mutts by killing one and protecting Clay while Elena hunted down the last mutt. He got Wyoming for territory as a reward.
Karl meets Hope Adams, a half demon under the illusion that she is working on behalf of the Interracial Council. Karl shows her that she is actually working for a cabal sorcerer, who has gone rogue. Hope and Karl also begin to date.
Karl is only mentioned a few times in this book, after Elena asks he look over some burglary plans for them.
No Humans Involved Edit
Is seen towards the end of the novel, he helps with the final take down of the humans, because they had kidnapped Hope.
Personal Demon Edit
Due to mate and confidence issues, Karl is revealed to have told Hope to "date other men" after thet first slept together several months before the novel, leading Hope to misunderstand and be angry with him. Karl and the Cabal found Hope and her two kidnappers. Sonny was killed by Karl, at which point Jaz asked Hope to kill him. So that he could be with his brother, and not be taken by the Cabal. However, the Cabal moved in too fast and Karl stopped Hope from killing Jaz.
Jaz was taken into Cabal custody, and vowed to come for Hope. Karl and Hope reconcile during the novel, eventually becoming closer in love.
Living with the Dead Edit
Hope and Karl go to L.A. to see Hope's friend Robyn Peltier. They end up helping her with a murder investigation involving local clairvoyants. In one scene Hope is feeling an little bit insecure about herself after getting kidnapped, and asks Karl to bite her, which he refuses, they later decide to take time away from each other, Karl taking a job in Australia.
Lucifer's Daughter Edit
After a freed demon is thwarted at a Adams' Family sponsored museum event, Karl, in a shy sudden way, proposes to Hope. They become engaged.
Karl is mother-hen to his pregnant and vision exhausted wife, even within Cortez Cabal protection. Karl almost dies from gunshot wounds, trying to thwart a religious cult kidnapping Hope to summon Lucifer. Near the end and while confined to a wheelchair, he stubbornly participates in the rescue mission and temporarily becomes possessed by Lucifer upon his daughter's birth.
Karl, alongside his family is mentioned to be seeking shelter with the pack abroad.
Life After Theft Edit
Hope is once again pregnant, she and Karl work on a theft that framed Karl which leads to an improved chaotic-balanced life for their family.