A seasoned fighter nonetheless, Cullen Sangerye lacks the particular skills necessary when it comes to the Sangerye Family business — hunting monsters.
Despite being a member of the Sangerye family, Cullen initially rejects violence and is afraid to face the Jinoo in any attempt to cure them using the Fiif'no Serum; his fear eventually means that Blink must step in to cure a Jinoo when he is unable to do so out of fear.
Cullen teams up with Blink in Harlem where the two track down Jinoo and attempt to cure them. As a result, Cullen is present when Blink is injured by Miss Knightsdale and subsequently begins transforming into an unknown creature.
After Berg becomes infected, Cullen suggests they seek the help of their uncle Enoch Sangerye as the roots do not appear to be working. Blink immediately rebukes Cullen, citing that he is the reason their parents were killed. Nonetheless, Cullen wins the battle and he leaves Harlem to find his uncle Enoch.
Upon finding him, Cullen is attacked by numerous little red creatures that Enoch eventually remarks are his guard dogs. Cullen explains the situation and asks if Enoch can help. He believes he can and the two head back to Harlem. On their way, however, they are attacked by Jinoo and Guardians, and Cullen is pulled through a Gateway and thought lost forever. Inside the other dimension, however, Cullen finds himself greeted by someone who refers to him by name, but he is unaware of who this is.
Eventually, Cullen makes a reappearance in Harlem when he — and the unknown figure — make their way back through a gateway to aid the Sangerye's in their fight against Doctor Sylvester. It is here where it is revealed that the other figure is none other than the Sangerye's mother, Nora Sangerye.
Time in Barzakh
Whilst little is known about Cullen's time in Barzakh, it is known that he contributed to the protection of the citizens within Barzakh and for preventing many of the Inzondo and Jinoo for ravaging Earth. At every opportunity that he tells his mother, Nora, and his father, Charlie, that he wishes to return home to Earth and will find a way.
Despite numerous conversations with Nora, Cullen is adamant that he wishes to return home and, during a battle in Barzakh, he spots his opportunity. Cullen voluntarily leaves his father Charlie behind as he and his mother return to Earth to aid the rest of the Sangerye family in their fight against the evils of Barzakh.
Upon his return, Cullen is much changed by his time in Barzakh and Ma Etta wonders if he can be trusted. She asks Nora about his time in the realm but she largely brushes Ma Etta off. Nonetheless, Cullen leaves Harlem to travel and cure Jinoo with Ford in an effort to avoid facing the fact that he left his father behind in Barzakh to die.
Fighting the Jinoo
Eventually, Cullen faces his father, Charlie, and returns to Harlem with Ford. Cullen and the remainder of the Sangerye family attempt to control the Jinoo and Inzondo problem but find that their efforts are futile. They do, however, find that Enoch's pets are able to somehow hold back the infectious trees that have taken over Harlem. They use this to their advantage as they continue to search for a permeant cure.