Who is he?
The Frogman is the main antagonist of Gray Cells. He has the power to alter his victim’s perceptions of reality and uses this ability to create a fantasy world for the children he abducts. This ability helps protect his identity and keeps him from being discovered. By creating a frog-like appearance, no-one believes the children who have seen him. At best, the adults treat him as an urban legend, at worse, they ignore him completely.
A powerful psychic, he can also use his abilities to control his victims, making them do his bidding. As the story develops, his vile motivations and reasons for abducting the children are slowly revealed as he attempts to bend kidnapped Joshua Glass to his will.
The Frogman is an amalgam of serial killers, with his psychic abilities substituting for the sinister charm attributed to people like Charles Manson or Ted Bundy. While his base personality is unnatural and unsettling.
The abductions themselves are closer to the Atlanta Child Murders with the early reluctance to investigate, the confusion about who could be committing the murders, and the conspiratorial element that there was more going on than the official story.
Why a frog? In Slavic mythology, a Vodyanoy is a water spirit who drowns people who anger him. Local unexplained disappearances were often attributed to Vodyanoy.
It was also designed as a disguise for the villain. Something, that in his mind, would be appealing to his victims. A sort of corrupted Kermit the Frog. Even in his human form, we wanted him to retain some of that otherworldly nature.
For most of the story, he is obscured, either in his frog form, or hidden in shadow. Only as young Josh attempts to break free from his control do we see snippets of his true appearance.