Fear Itself event, where she nearly succeeded in burning the world to cinders.
Sinthea Schmidt first appeared, albeit as a child, in Captain America #290 in February 1984. She was co-created by the celebrated writer J.M. DeMatteis and artist Paul Neary during their influential run on the title. Her initial introduction was part of a long-term storyline designed to delve deeper into the twisted psychology of the Red Skull, exploring his desire for a legacy and an heir.
Her character underwent a significant transformation, being artificially aged into an adult and introduced as the menacing leader of the “Sisters of Sin” under the new moniker Mother Superior. This evolution allowed her to become a direct physical and psychological threat to Captain America. Over the decades, writers such as Ed Brubaker and Matt Fraction would further develop her character, removing the psionic powers of Mother Superior and recasting her as a more grounded, yet equally sadistic, martial artist and strategist named Sin. It was Brubaker's run that cemented her modern identity as a core antagonist in the Captain America mythos, making her a co-architect of his death and a chilling reflection of her father's evil.
Sinthea Schmidt's origin is a tragic and horrifying testament to the Red Skull's monstrous nature. Desperate for a male heir to carry on his Nazi ideology and legacy, Johann Schmidt fathered a daughter with a local laundress. Disgusted and enraged that he had produced a girl, he nearly killed the infant. His follower, Susan Scarbo (later known as Mother Night), convinced him that the child could still be of use. Schmidt agreed and decided to raise his daughter himself, indoctrinating her from her first breath with the hateful, nihilistic philosophies of HYDRA and the Third Reich. He named her Sinthea. The process was brutal. To accelerate her indoctrination and turn her into a weapon, the Red Skull used a special machine to artificially age Sinthea into adulthood in a matter of moments. Her mind was filled with psionic knowledge and her body was honed into a lethal weapon. Reborn as Mother Superior, she was given command of a group of orphaned girls who had been similarly brainwashed and empowered, naming them the Sisters of Sin. As Mother Superior, Sinthea possessed formidable telepathic abilities, including the power to control minds, project illusions, and fire psionic blasts. She became a formidable adversary for Captain America, leading the Sisters of Sin in numerous terrorist acts. Her reign as Mother Superior came to an end when she was captured by S.H.I.E.L.D.. During her incarceration, she was treated by psychologists and subjected to a process that reversed the artificial aging, restoring her to her proper chronological age as a young girl. The traumatized Sinthea was sent to a re-education facility, seemingly stripped of her brainwashing. However, the evil implanted by her father was not so easily erased. Years later, a new Red Skull (a Russian operative named Albert Malik) sent his agents to find her. Their plan was intercepted by one of Johann Schmidt's primary agents, Crossbones (Brock Rumlow). Crossbones rescued Sinthea, re-kidnapped her, and brought her to his master. Under her father's influence once more, Sinthea was retrained and re-brainwashed. This time, however, she was not artificially aged. Instead, Brock Rumlow, a brutal but effective teacher, personally trained her in espionage, demolition, firearms, and hand-to-hand combat. The two developed a deeply sadistic and romantic relationship. Taking the simple, brutal codename Sin, she emerged as a non-superpowered but highly lethal terrorist, serving as her father's second-in-command. Her path took another dark turn when she attempted to assassinate Captain America at the conclusion of the Civil War. While Crossbones fired the first shot, it was a hypnotized Sharon Carter who fired the fatal bullets. During the ensuing chaos, Sin was severely injured by a stray explosion. When she was later rescued by her father's forces, she was left with horrific facial scars that mirrored the grotesque “red skull” visage of her father, a physical manifestation of the monster she had become. Fully embracing this new identity, she often wore a red mask and, for a time, even became the new Red Skull after her father's consciousness was trapped in a robotic body.
Sinthea Schmidt, or Sin, does not exist in the Marvel Cinematic Universe.
The MCU's primary antagonist for its Captain America arc is her father, Johann Schmidt, the Red Skull, who first appears in _the_first_avenger. The film establishes his backstory as the head of HYDRA during World War II and his obsession with the Tesseract. His story seemingly concludes at the end of the film when the Tesseract teleports him across space.
He makes a surprise return in _infinity_war and _endgame as the spectral, cursed Stonekeeper on the planet Vormir, tasked with guarding the Soul Stone. In this role, he is more of a cosmic entity than an active villain, a prisoner of the artifact he once sought to control. Throughout his entire MCU arc, there is no mention of a wife, lover, or any children.
The decision to omit Sin from the MCU can be attributed to several narrative and thematic reasons:
Sin's capabilities have evolved significantly throughout her history, shifting from psychic powerhouse to master combatant and, for a time, a dark goddess.
During the Fear Itself event, Sin lifted the mystical Hammer of Skadi, becoming one of the “Worthy,” the heralds of the Serpent. In this form, her powers were magnified to a cosmic scale:
Sin is a study in pure, cultivated evil. Unlike her father, whose ambition was rooted in a twisted sense of order and fascist ideology, Sin's primary motivation often appears to be a nihilistic desire for chaos and destruction. She is sadistic, cruel, and takes immense pleasure in inflicting both physical and psychological pain. Her entire identity is defined by her father. She simultaneously worships him and desperately seeks to earn his approval, while also harboring a deep-seated desire to surpass his legacy of terror. This creates a volatile and complex dynamic. Her relationship with Crossbones was one of the few seemingly genuine connections in her life, a bond forged in shared violence and sadism. After his death, her capacity for destruction only grew, unburdened by any remaining attachments. She is, in essence, a true believer in the religion of hate her father created for her.
Sin typically utilizes a wide variety of conventional weaponry. She has no standard costume but often favors practical combat attire.
As Sin does not exist in the MCU, she possesses no abilities, equipment, or established personality within this continuity. The villainous traits associated with her comic character—unwavering loyalty to HYDRA, exceptional combat skill, and a personal grudge against Captain America—are primarily embodied by the MCU version of Crossbones.
Fear Itself, the Serpent chose Sin to be his primary agent on Earth, anointing her as Skadi. Sin served him with religious fervor, seeing his apocalyptic vision as the ultimate fulfillment of her own destructive desires.Fear Itself, as Skadi, she beat him to the brink of death, an event that led to Bucky faking his own death and returning to his Winter Soldier identity. Their battles are vicious, with Sin often mocking him for his past as a brainwashed assassin.Fear Itself, she was the de facto field leader of the Serpent's avatars on Earth, a group that included powered-up versions of The Thing, Juggernaut, and Titania.This is arguably Sin's most defining storyline. Working directly under her father, the Red Skull, Sin and Crossbones orchestrated the public assassination of Steve Rogers on the steps of a federal courthouse. Crossbones acted as a sniper to create a diversion, while Sin coordinated with Doctor Faustus to ensure a brainwashed Sharon Carter was in position to fire the fatal shots at point-blank range. Sin's role was not just that of an enforcer; she was a key field commander in the complex plot. Her actions directly led to the death of an icon and plunged the entire Marvel Universe into a state of shock and mourning, cementing her status as a top-tier villain.
Seeking a weapon of ultimate power, Sin located the forgotten Hammer of Skadi in a hidden Nazi base in Antarctica. Upon lifting it, she was transformed into Skadi, the Herald of the Serpent, an ancient Asgardian god of fear. Wielding immense power, she became the Serpent's vanguard, leading his forces in an all-out assault on Washington, D.C. Her rampage was nearly unstoppable. In one of the event's most shocking moments, she brutally defeated Bucky Barnes, the Captain America of that time. The public believed Bucky was killed in the battle, forcing him to go underground once more. Sin's time as Skadi represented the peak of her physical power and her closest brush with total victory, as she nearly brought the United States to its knees.
Following the discovery that Steve Rogers was not dead but was in fact lost in time, Sin and the Red Skull's forces worked tirelessly to prevent his return. While the Red Skull (in a new body) attempted to hijack Steve's mind as he returned to the present, Sin led the ground-level operations to stop the Avengers. She engaged in a fierce battle with the New Avengers, demonstrating her deadly combat skills and unwavering resolve. Though she ultimately failed to prevent Steve's return, the storyline highlighted her capabilities as a field leader and her fanatical devotion to her father's cause.
In this more recent storyline, Sin returned to a purer form of villainy, forgoing cosmic power for psychological warfare. She orchestrated a campaign of terror and misinformation aimed at fracturing an already divided America. By manipulating media and staging false flag attacks, she sought to incite a new civil war, proving that she had learned from her father that the most potent weapon is often fear and distrust itself. This arc showcased her evolution from a blunt instrument of violence into a sophisticated manipulator, a true daughter of the Red Skull.
All-New Wolverine, Sinthea Schmidt has become the President of the United States. She is a ruthless tyrant, continuing her villainous ways on a political stage.