Monstrilio (2023) is a debut literary horror novel by Mexican artist and writer Gerardo Sámano Córdova. When 11-year-old Santiago dies, his mother, Magos, cuts his body open and removes a piece of his lung, which she keeps in a jar and feeds until it grows into a furry, carnivorous monster called Monstrilio. Magos, her husband, Joseph, and her best friend, Lena, quickly bond with the creature, despite its voracious appetite for flesh. Eventually, Monstrilio develops a human body that resembles the deceased Santiago, but his carnivorous tendencies remain. Monstrilio explores Humanity Versus Monstrosity, The Fear of Love Being Conditional, and Family Dynamics in the Face of Grief.

This guide uses the 2023 Zando Kindle edition.

Content Warning: The source material and guide feature depictions of child death, disordered eating, animal cruelty and death, graphic violence, sexual content, cannibalism, and death. The Background section contains a brief reference to death by suicide.

Plot Summary

Magos and Joseph’s son, Santiago, is born with just one lung. The doctors don’t expect the baby to make it home from the hospital, but he lives until he is 11 years old.

Santiago dies in his bed in Upstate New York, surrounded by his mother and father. Joseph cries openly, but Magos is struck by the sense of anticlimax of her son’s death. When she is alone with his body, she cuts him open, wanting to keep a part of him that most reflects his “Santiagoness.” She cuts off part of his lung and places it in a jar. Joseph is horrified by the way Magos mutilated their son’s body and by her lack of visible grief.

After weeks of “haunting” one another in their shared house, Magos leaves Joseph and goes back to Mexico City, where she stays with her mother, Lucía. Her mother’s housekeeper, Jackie, finds the piece of Santiago’s lung and tells Magos a story about a woman in her hometown who cut out a girl’s heart and fed it until it grew into a man. She warns Magos against feeding the lung, but that night, Magos spoons a little chicken broth into the lung’s jar. In the morning, she is shocked to see that the lung has absorbed all of the broth.

Magos keeps the lung hidden in her room as it grows into a frisbee-shaped, furry creature with a wide mouth full of sharp teeth and an “arm-tail” appendage. One night, the lung escapes and attacks the family dog, frightening Jackie. Magos pries the creature’s teeth off the dog’s thigh and makes Jackie promise not to tell Lucía about the lung.

Telling Joseph that she has something of Satiago’s that she wants to show him, Magos convinces her husband to come to Mexico. She shows him the lung, but while they are arguing over what to do with the creature, it escapes and attacks Lucía. Jackie and Magos’s friend Lena come to help, and Joseph strikes the creature with a hammer despite Magos’s protests. Believing the creature to be dead, Magos breaks into tears for the first time since Santiago’s death and flees with the creature’s body, which she leaves in a nearby park.

After the lung’s attack, Magos moves in with Lena and falls into a deep depression. However, when Jackie comes over to report that the lung has been sighted in their neighborhood, Magos perks up immediately. She recruits Lena and Jackie to search for the creature, which they find in a nearby park with the carcasses of two cats. Magos brings the lung back to Lena’s apartment, despite her friend’s misgivings. Joseph resurfaces after leaving town in the aftermath of the lung’s attack, and is surprised to find Magos and the lung living with Lena. When the lung sees Joseph, it speaks for the first time, calling him “Papi.”

Magos, Joseph, and the lung, now called Monstrilio, soon move back into their old Mexico City apartment. Monstrilio continues to grow, and his vocabulary expands. However, he is still wild: He gives Joseph a nasty cut that requires stitches, and he once escapes to massacre neighborhood pets. Magos becomes convinced that Monstrilio’s arm-tail is the source of his wildness, and that amputating it will allow him to “evolve.” Lena and Joseph oppose the operation, but Magos persuades Lena, a surgeon, to perform it. Without his arm-tail, Monstrilio falls into a deep depression, becoming lethargic and despondent. Lena and Joseph are wracked with guilt. They want to put Monstrilio out of his misery, but Magos kicks them out of the house.

Eventually, Monstrilio sheds his monstrous form and grows into a boy whom Magos calls “Santiago,” and everyone else refers to as “M.” Lena moves to New York, and Joseph and Magos divorce. Joseph also moves to New York and, after a number of years, starts dating a man called Peter. Magos becomes a successful performing artist and moves to Berlin with M to work on a new art piece. Joseph and Peter become engaged, but Joseph is unable to disclose to Peter the truth about M’s history.

M is now a young man, and Magos gets him a job at a gallery, where he meets Thomas, who becomes his boyfriend. M is slowly adjusting to human life, except for his appetite. He is constantly hungry and desperately craves human flesh. The first time he has sex with Thomas, he gets so hungry that he bites the other man. He promises not to do it again, and Thomas forgives him.

Magos invites everyone to the premiere of her new show in Berlin. It is called Son, and involves Magos sobbing uncontrollably on stage while holding the pajamas that Santiago died in. M is in the audience and hurries out before the show ends. Joseph and Lena are horrified by the performance, and Peter, who doesn’t understand the context, is confused. Joseph, Lena, and Magos return to Magos’s apartment to find that M has eaten the neighbor and his cat. The neighbor is still alive, so Magos and Lena rush to call an ambulance while Joseph hurriedly cleans M, dresses him, and smuggles him out of the apartment building.

M returns to New York with Peter and Joseph and stays with Joseph’s Uncle Luke. He gets a job at a used bookstore and makes a friend who calls his desire to bite a “kink” and helps him set up profiles on dating apps. M starts going on dates with men who allow him to bite them, but these tiny tastes of blood leave him far from satisfied. Then M gets a message from a man named Sam, who believes being consumed by a god will transport him to another realm, and asks M to eat him. When the newspapers report on a crime scene with human bones “picked clean” of flesh, M’s family immediately knows what happened. Again, they rush to hide any evidence of M’s involvement. Amid his struggle to suppress his appetite and be the human boy Magos and Joseph believe him to be, M notices that his arm-tail is growing back.

For Peter and Joseph’s wedding, the family returns to the house where Santiago died. The night before the wedding, M knows he is ready “to give the wildlife a try” (322). He wakes his family members one by one, bidding farewell first to Uncle Luke, then to Lena, Magos, and Joseph. He takes his clothes off, folds them carefully, and lets his fangs and arm-tail go free as he steps forward into the dark forest.