Although he appears human, Professor Carcosa is not who he seems to be. Part of a pagon coven, Professor Carcosa comes to greendale with some ill intentions. Ruthless and determined, Greendale seems to be the perfect place for his plans.
Otherwise known as the Great God Pan, Carcosa was the leader of the pagan tribe who moved to Greendale with the goal of raising their god. Carcosa is also the owner of Professor Carcosa’s Traveling Carnival and Phantasmagoria. The tribe of which he was leader succeeded in raising their god and for a time that god, called The Green Man, ruled over Greendale. However they were thwarted and Carcosa killed when Sabrina went back in time. Carcosa is a creature known as a satyr, which is half goat, half man. His personality is described as ruthless and determined to raise The Green Man. This caused him to subject his own tribe to sacrifice in the rituals they performed to the old gods when no one showed up to the carnival. In his human form, Carcosa wears gentleman's clothes, has brown shoulder length hair. However, when the glamour that is his human form is off, he is a satyr with hairy legs, cloven hooves, and a human face with a goatlike features with horns. He was later killed by Prudence Blackwood when Sabrina went back in time and stopped The Green Man. Prudence killed him by stabbing him in the back with her sword.
Due to being a satyr, Professor Carcosa has his own set of abilities. These include; Insanity gaze, a power that allows his gaze to turn a person insane upon looking at them. However, this ability did not work on Rosalind Walker as her cunning protected her from its effects. Another power Carcosa has is Glamour, which allows him to hide his true form. He uses this to appear human. The last power is Longevity, the extent of it is unexplored however. He is described as one of the oldest pagan monsters.
Upon arriving in Greendale, the carnival hosts an opening night. Rosalind Walker, Robin Goodfellow, Harvey Kinkle, and Theo Putnam attend it. Rosalind, as a seer is able to use her cunning to see through the glamour Carcosa uses to hide his true form.
During the carnival, Carcosa challenges Harvey to the Strongman game. Harvey accepts this but fails to hit the target hard enough to ring the bell. He walks away embarrassed, which Carcosa notices. After the carnival, the Phantasmagoria holds a ritual. They dig a hole while Nagaina and Circe reveal they can smell the innocence on Harvey and Mary Wardwell. Robin adds that Theo is also innocent, or a virgin. Carcosa tells the tribe that Rosalind is a seer and therefore a threat to him. Nagaina offers to take care of Rosalind. Once the hole is dug they plant a flower. One of the attendees of the carnival is then sacrificed. They chant as Carcosa prays to the old gods.
After this, Professor Carcosa leads his coven into the woods to prepare to celebrate Ostra. It is here they meet The Church of Night for the first time. During this interaction, Carcosa asks Zelda and Ambrose how long they have been in greendale. The two reply that they have been in Greendale for many generations starting from the old country. Zelda asks Carcosa where his people come from and guesses they are drifters. She inquires if they will be moving on soon. Carcosa tells her there’s something about the area that makes him want to set down roots. An argument breaks out after Dorcas is bitten by a snake.