Allie is a 14-year-old girl from Cape May, New Jersey, who finds herself trapped in the spirit world of Everlost after a car accident. She is highly pragmatic and deeply logical, making her naturally skeptical of the strange new world and its unspoken rules. Determined and goal-oriented, she immediately focuses on finding a way to return home to the living world. Her forceful personality and refusal to accept things at face value occasionally bring her into conflict with authority figures.

Nick is a 14-year-old boy of half-Japanese descent who wakes up in Everlost alongside his fellow crash victim, Allie. Due to the nature of their arrival, his face is permanently smeared with the chocolate he was eating when he died. Initially pessimistic and anxious about their situation, he prefers to follow rather than lead. Over time, he learns to assert himself and question the established order of the spirit world.

Lief is an 11-year-old boy covered in freckles and wearing old-fashioned clothing, indicating he has been in Everlost for over a century. Having lost most of his memories, including his real name, he lives a solitary but peaceful existence in a dead forest. He is remarkably adaptable to new situations but harbors a deep fear of being abandoned by the rare friends who pass through his territory.

Mary Hightower is a 15-year-old Afterlight who serves as the self-appointed mother figure and spiritual leader to hundreds of children living in the Everlost version of the Twin Towers. Dressed in an emerald green velvet dress, she is elegant and highly composed. She writes instructional books to help new arrivals adjust to their half-existence and firmly believes that Everlost is a permanent home where children belong.

The McGill is a grotesque, notorious monster who captains a ghost pirate ship called the Marine Sulphur Queen. He possesses a lobster-red, pockmarked complexion, claws instead of hands, and wildly mismatched eyes. Obsessed with his fearsome reputation, he kidnaps Afterlights and hangs them upside down like wind chimes, hoping to collect a thousand souls to fulfill a mysterious fortune cookie prophecy.

Mikey is Mary Hightower's younger brother. He and Mary died in a train accident on their way home, ending up together in the dark tunnel between life and death. According to Mary's historical account, he sank deep into the Earth upon returning to the living world and discovering their father had moved on and remarried.

Vari, short for Stradivarius, is a mousy boy with curly blond hair who acts as Mary Hightower's right-hand assistant in the Twin Towers. He plays the violin and is fiercely devoted to Mary, often acting as a gatekeeper between her and the other Afterlights. He resents anyone who threatens his close proximity to Mary.

Speedo is a 13-year-old Afterlight who works as a Finder in New York. True to his nickname, he constantly wears nothing but a swimsuit. He specializes in waiting patiently at events in the living world for items to cross over into Everlost, trading these rare commodities to Mary Hightower for other goods.

Johnnie-O is the aggressive gang leader of a crew of Afterlights known as the Altar Boys. He and his gang roam the areas outside the city, intercepting newcomers to search them for valuable objects or force them into servitude. Despite his tough exterior, he is highly superstitious and fearful of both the McGill and fortune cookies.

The Haunter is a powerful Afterlight who appears as a small six-year-old boy surrounded by a yellowish glow. Operating out of an old pickle factory, he is one of the few beings who possesses Criminal Arts, including the rare ability to pull objects from the living world and teach others how to possess the living.

Pinhead is a pirate Afterlight and the chief officer aboard the Marine Sulphur Queen. Once a member of a rival gang called the Twin Pier Marauders, he betrayed them to free the McGill and now serves as his loyal second-in-command, overseeing the ship's grotesque crew.

Meadow is a friendly Afterlight living at the base of the Twin Towers. She acts as a welcoming guide for newcomers arriving in the city, introducing them to the local customs and eventually leading them to Mary Hightower.

Skelly is an Afterlight boy who permanently wears a skeleton costume. He provides Allie with crucial information about the Haunter and the concept of skinjacking, acting as an informant for those seeking answers outside of Mary's official teachings.