In the 1700s, nearly 200 years after the death of Gottskalk Nikulausson, Loftur allegedly deciphered the clues hidden by a secret society tied to the Church of Holar and discovered Gottskalk's hidden tomb. He removed the Rauoskinna from the tomb and attempted to leave Iceland with it. He was attacked by the Spirits of the Ocean due in part to a spell of protection cast on the book by Gottskalk. In 1722, Loftur was presumed lost at sea. The Rauoskinna washed ashore and was returned to the tomb.  
In truth, Loftur did not die. Instead, he discovered the secret of immortality.  Culling other humans. Loftur circumvented the deal with The Devil he made prior through the discovery and his culling allowed him to elude the Devil for centuries. However, he never found the Rauoskinna. He kept tabs on Egon Spengler ever since he first searched for the Rauoskinna in his college years.  He came to believe the Ghostbusters were the only way he could bypass the Rauoskinna's defenses and came up with a plan to enlist their services without them knowing it.  Loftur secured the Ghostbusters' assistance slyly through his proxy Erland Vinter.  Loftur was not pleased with Vinter's results and decided to approach Egon directly. Just as the Ghostbusters concluded their case in Ireland, Loftur went to Egon's Apartment. He presented a story that while he was at Ray's Occult Books, Eduardo Rivera informed him Egon was looking for a copy of The Johansen Argument. Egon realized Eduardo didn't have his address and asked how he found him. Loftur eyes glowed red and he cryptically answered "magic." Egon fired his Psychokinetic Defibrillator point blank in Loftur's face. Since Loftur was not possessed, the Defibrillator had no affect on him at all. Loftur sent Egon flying across his apartment. Loftur formally introduced himself and verified reports of his death in 1722 were false. Egon wasn't buying that Loftur would wait to long to show himself and released the Gulper Ghost from the Paranormal Containment Research Tank. The ghost flew through Loftur and coated him in slime. Loftur was mostly disgusted. Egon called him a coward for trying to manipulate the Ghostbusters into locating the book. Loftur admitted he should have been direct but felt threatened. He went so much as to claim they were kindred spirits then asked Egon to help him locate the Rauoskinna with the promise of learning so much from owning the Devil. Egon refused. Loftur decided to give Egon the chance to rethink his answer and atomized him.
Kaia May went to the Firehouse and revealed to them that Vinter served Loftur. She then passed along their new demand, find the Rauoskinna for them and Egon would be restored. She gave them a list of possible locations of the key and map to the book. Before she left, Kaia admitted she didn't think neither Vinter or Loftur could be trusted and advised them to destroy the book when they found it. Vinter and Loftur awaited in the former's office in Oslo, Norway for the results of the Ghostbusters' flight to Iceland and subsequent search for Gottskalk's tomb in. Loftur changed his mind and ordered Vinter to change the standing orders to let the Ghostbusters leave Akureyri with the Rauoskinna and return to New York. Vinter was visibly frustrated with the sudden alternations to the original plan. Loftur asked Vinter if he disagreed with the new instructions. Vinter admitted respectfully that he thought Loftur complicated things by attacking Egon Spengler and giving the rest a reason to retaliate. Loftur stood and walked over to Vinter, admitting he had not learned the value of patience despite his long life. He snapped Vinter's neck but noticed he left him within an inch of his life. Vinter could only watch as Loftur pulled a knife and culled his body. Now, as Vinter, Loftur phoned his secretary Astrid and asked her to book a flight to New York. He left Norway the next day.
A day and a half later, Loftur called the Firehouse. Kevin Tanaka called the upstairs lab's phone and told Ray Stantz someone called saying he's the guy who visited Egon Spengler. Kevin put Loftur through to Ray. Loftur cut off Ray mid-sentence and told him to turn over the Rauoskinna and he would reunite him with Egon. Loftur checked his watch and noted it was 5:48 pm. He told Ray to meet precisely at midnight in Central Park near Umpire Rock then he hung up. A little later, Loftur sat down on a park bench. A young girl saw his Ley Lines book and remarked to her mother how big it was. Loftur asked her if she knew what it was about. She didn't. Loftur told her it was about magic and asked if she believed in it. The mother told her daughter it was time for dinner and they should leave him alone to read his book. Loftur lamented there was no belief in magic anymore but declared that would change soon.
Loftur was impressed with the Ghostbusters' punctuality and the extra manpower they brought along. Ray demanded Egon's return and held a lighter to the Rauoskinna. Loftur didn't care and blasted the lighter out of his hand. Special Agent Melanie Ortiz took a shot but Loftur easily blocked the Proton Stream with a rune. Jenny Moran concluded they needed to fight fire with fire and read a spell from the Rauoskinna aloud. Loftur became annoyed with Jenny's bumbling attempt at sorcery. Everyone except Winston was teleported to Hell. He sighted The Devil approaching them and was overcome with desperation. He promised to bring everyone back to Earth if they gave him the book and he would even return Egon as agreed. The Ghostbusters opted to put some distance between themselves and Loftur as the Devil and Hell's Demons got closer and closer. The Devil conjured their contract. The demons converged on Loftur and he blasted at them in vain. They ravaged him and reduced him to a charred corpse. The Devil remembered the Ghostbusters as the ones who helped Stingy Jack but he overlooked that transgression for the delivery of Loftur to him. He gave them permission to leave then pulled Loftur's soul from the corpse. The Devil promised they were going to have fun together and admonished Loftur for trying to cheat him.
Loftur was a sorcerer according to legend. He is also immortal and has managed to live for almost 300 years. One magic spell used on Egon appeared to resemble telekinesis while another atomized Egon through some form of accelerated cellular dispersal.
- On page 4 of Ghostbusters International #5, panel 2, one of the words written on the board is "Staðastaður." In the folktale about Loftur's death, he felt like he would die on a certain Sunday after an encounter with Gottskalk's ghost. His friends advised him to see a priest in Staðastaður. He stayed with him until a Sunday but after the priest went to perform last rites, Loftur went out on a fishing boat and was pulled underwater.
- On page 5 of Ghostbusters International #5, Loftur's last name is misspelled a "B" instead of a "Þ" as well as other minor lettering issues with Icelandic terms and names.
- On page 5 of Ghostbusters International #5, in panel 4, the rune that Loftur finds is the Ægishjálmur (or Helm of Awe), an Icelandic magical stave said to induce fear and to protect against abuse of power.
- The story of Loftur's search for the book and being dragged underwater from his fishing boat was the subject of actual legend. Some claim it was suicide instead. He was never heard of after 1722 according to record.
- In the what came before! page of Ghostbusters International #8, the spelling of Loftur's last name is poked fun at.
- In the Dramatis Personae of Ghostbusters International #10, Loftur's last name is spelled differently a third time. The second "o" in Thorsteinsson is replaced with an "e". 
- On page 18 of Ghostbusters International #10 and on, Loftur does not use Erland's reading glasses.
- On page 3 of Ghostbusters International #11, in panel 2, the rune Loftur casts is the Ægishjálmur (or Helm of Awe) - said to protect against abuse of power or induce fear.
- On page 4 of Ghostbusters International #11, Peter calls Loftur "Snorri" after Snorri Sturluson, author of the prose "Edda"
- Loftur was alluded to in Egon's bio on Crossing Over Virtual Trading Card #19. 
- Loftur was alluded to in Death's bio in Crossing Over Virtual Trading Card #36, released on June 21, 2018. 
- Ongoing Series
- Volume 3
- Ghostbusters Annual 2017
- Alluded to on Story So Far Page 
- Ghostbusters 101
- Teenage Mutant Ninja Turtles/Ghostbusters Volume 2
- Ghostbusters Annual 2018
- Alluded to on the What Came Before page. 
- Egon Spengler (2016). IDW Comics- "Ghostbusters International #5" (2016) (Comic p.5). Egon Spengler says: "The clues were deciphered nearly 200 years after Nikulausson's death by the sorcerer Loftur Þorsteinsson, who found the grave, and the book... but it was attacked by the Spirits of Ocean itself when he tried to leave Iceland with it."
- Loftur Þorsteinsson (2016). IDW Comics- "Ghostbusters International #7" (2016) (Comic p.18). Loftur says: "My name is Loftur Thorsteinsson."
- Egon Spengler (2016). IDW Comics- "Ghostbusters International #5" (2016) (Comic p.5). Egon Spengler says: "Loftur's body was never recovered - hardly unusual considering it was lost at sea during the 1700s. The book was said to have washed up onshore later, before being returned to Nikulausson's hidden tomb."
- Egon Spengler (2016). IDW Comics- "Ghostbusters International #7" (2016) (Comic p.18). Loftur says: "He died in 1722!"
- Loftur Þorsteinsson (2016). IDW Comics- "Ghostbusters International #7" (2016) (Comic p.18). Loftur says: "No, he merely discovered the secret of immortality."
- Loftur Þorsteinsson (2016). IDW Comics- "Ghostbusters International #7" (2016) (Comic p.18). Loftur says: "I've kept tabs on you, Doctor. Ever since your initial research into the Rauoskinna. I know you know all the legends... but I never actually found it."
- Loftur Þorsteinsson (2016). IDW Comics- "Ghostbusters International #7" (2016) (Comic p.19). Loftur says: "You know how the Rauoskinna is protected, yes? It's why I went to such lengths to enlist the Ghostbusters."
- What Came Before! Page (2016). IDW Comics- "Ghostbusters International #8" (2016) (Comic what came before! page). What Came Before! page reads: "He tried to get their assistance on the sly - by way of his proxy, Erland Vinter - but wasn't happy with the results."
- Dramatis Personae (2016). IDW Comics- "Ghostbusters International #10" (2016) (Comic Dramatis Personae). Biography reads: "Scandinavian industrialist and thrall of Loftur Thorsteinssen."
- TomWaltz Tweet 4/24/18
- TomWaltz Tweet 6/21/18
- Narrator (2017). IDW Comics- "Ghostbusters Annual 2017" (2017) (Comic Story So Far Page). Narrator says: "They were caught up in the plot of a centuries-old Scandinavian warlock, was was trying to escape a deal with the devil."
- Dramatis Personae, Egon Spengler (2017). IDW Comics- "Ghostbusters 101 #1" (2017) (Comic Dramatis Personae Page). Line reads: "Got killed by a nigh-immortal sorcerer once (and got better)."
- Egon Spengler (2017). IDW Comics- "Ghostbusters 101 #1" (2017) (Comic p.3). Egon Spengler says: "In my defense, I was recently atomized by a Scandinavian warlock."
- Ray Stantz (2017). IDW Comics- "Teenage Mutant Ninja Turtles/Ghostbusters Volume 2 Issue #1" (2017) (Comic p.3). Ray Stantz says: "Something like the Scandinavian warlock case."
- What Came Before page (2018). IDW Comics- "Ghostbusters Annual 2018" (2018) (Comic What Came Before page). Narrator says: "They went to Hell and back to keep a Scandinavian warlock from releasing the power of a cursed book, an experience that left one of their own - Jenny Moran - turned into a bona fide ghost."