He was approached by a band of humans who called themselves the “Marauders,” and was led to an underground prison of freaks. The Marauders had heard of his research, and thought that they could be of use to the geneticist, for a pretty penny. Essex was fascinated, but the Marauders turned against him before Essex convinced them to join him in his scientific cause.
In the sewers, a group of Marauders not with Essex stumbled upon the sleeping chamber of the eternal Apocalypse, who was awakened. He destroyed them. Before Apocalypse killed the Marauders, he was told of Essex. He too was intrigued at the man's science. He disguised himself as human and sought him out. Apocalypse allied himself with the man called Essex. He, after listening to Essex, realized that he was the first born mutant.
Elsewhere, Cyclops and Phoenix were sent by Madame Sanctity to 1859 London with a new mission. This time they dwelled within their own bodies, but Cyclops was without his visor. He had no alternative but to keep his eyes shut lest he unleash the destructive force of his optic blasts. He awoke in the sewers amongst the imprisoned freaks and their captors, the Marauders. Phoenix found herself within a church.
Sanctity guided Phoenix to Milbury House, home of Nathan and Rebecca Essex. Cyclops and Phoenix communicated via their telepathic link. Jean arrived to witness Rebecca Essex burying her dead newborn son on her estate. The son had been dead for quite some time and was thought previously by her to have already been buried at his gravesite. Rebecca had only just discovered that her husband had been hiding the body and studying it during the time following its death. Rebecca told Jean that the death of their son had driven Nathaniel insane.
Rebecca led her to their basement where Nathaniel held some of the Marauders’ freaks captive for his research. They discovered that Nathaniel Essex had gone to a place called the Hellfire Club. Apocalypse, also present at the club, revealed his plan of conquest to all those present, including Nathaniel. The members saw Apocalypse as a buffoon. Furious, Apocalypse revealed his true form and killed a few of the members to make his point.
Cyclops escaped the Marauders and found Jean. Apocalypse attacked the two reunited heroes. Essex was forced at one moment to decide whether he would join Apocalypse to achieve his scientific goals. Apocalypse imprisoned Cyclops. Jean, too, was trapped while attempting to free Scott.
Meanwhile, Nathaniel’s wife, Rebecca, died blaming him for what happened to their son. Unable to escape the guilt over his wife’s death, Essex accepted Apocalypse’s offer and was transformed into Mister Sinister. In this new form, he was immortal. Essex was assigned to create a pestilence that would help Apocalypse cull the weak from the strong. Scott and Jean escaped their imprisonment.
Apocalypse, at Bukingham Palace, attempted to destroy the Royal Family when Scott and Jean intervened. Sinister, perhaps still weighed by his own conscience, poisoned Apocalypse with the pestilence that he made, affecting the salvation of Scott and Jean. This action also may have had implications to further Sinister’s own agendas as well, since making the plague for Apocalypse would possibly result in the destruction of future generations that might show signs of mutations.
Apocalypse was aware of what Sinister had done. Nur found strength in his servant for what he did, and so let him live. Scott and Jean were returned to the present in the 20th Century [[[[[Some of Essex’s freaks become what would be ancestors to the Summers family.]]]]] (THE FURTHER ADVENTURES OF CYCLOPS AND PHOENIX #s 1-4).
During the Second World War, the Nazi scientist Nathaniel Essex held a special interest in the superpowered group the Invaders. On an occasion when the mutant Sub-Mariner fought in his midst, Essex managed to obtain a specimen of blood from the injured hero.
When United States officer John Greycrow was executed for killing and scalping his fellow soldiers, Sinister was waiting by his gravesite when the mutant that would be Scalphunter emerged from his grave. He recruited him.
Essex re-routed a train destined for the death camps to his own lab; the bodies of its passengers he used to further his creation of a clone of the Sub-Mariner. The clone faced off and held its own against the original and each of the Invaders save Captain America, who killed it (WEAPON X #14).
Near to the end of the Second World War, an American officer named Thorton, otherwise nicknamed "the Professor," discovered within the basement of an occupied Nazi facility an abandoned lab once used by Nathaniel Essex. Using the information on mutants found in a journal left by the scientist, the Professor would further his own experiments culminating in the Weapon X Program (WEAPON X #23).
Mister Sinister, always opposing his master, once aided the Thieves Guild in finding the location of one of Apocalypse’s abandoned citadels in Egypt. The External Candra, tied to the Guild, had use for any information regarding Apocalypse.
A time-displaced Gambit caught up with Sinister, who had abducted his mutant friend Courier for experimentation. In exchange for the means to go after the Thieves Guild and for the freedom and health of Courier, Gambit gave Sinister a piece of Courier’s unique malleable flesh. Sinister used this specimen to alter his own physiology, greatly empowering him forevermore. From it he’d derive a way to shape-shift and clone people.
Gambit, Sinister, and Courier found the Thieves Guild and Candra, who had since encountered and imprisoned Apocalypse’s slave Ozymandias. They were using the information inscribed on the walls of the underground stronghold to perform spells that would give Candra immense power. Sinister and the others put an end to the Guild’s scheme and Candra was turned over to the Externals to serve punishment for what she had tampered with. Gambit intrigued Sinister, but they parted ways (GAMBIT #s 13-14).
Sinister, referred to locally as the enigmatic "White Devil," began his association with Sabretooth through Scalphunter in Vietnam in 1968. Sabretooth was being paid to investigate Sinister's covert experiments in that country; Scalphunter met his employer's price and Sabretooth desisted from his inquiry (WEAPON X #27).
Amanda Mueller, the Black Womb, obtained babies of genetic intrigue and held them at the Eugenics Information Center. Alex Ryking, Dr. Kurt Marko, and Destiny were involved. Though never meeting her face-to-face, “she provided [them] with nearly unlimited means—to map out the growing advancement in human evolution.” For what purpose and for whose benefit she did this was uncertain, yet among the suspects was one most sinister (X-MEN FOREVER #4).
During the 1950s, Mister Sinister discovered the existence of a young Jean Grey. Assured that she was one of the keys to defeating Apocalypse, he planned to eliminate her parents and bring her to an orphanage he controlled in Nebraska. Before he was able to do so, Charles Xavier, the world’s preeminent telepath and eventual founder of the X-Men, recruited the girl for his school. His plans quashed, Sinister was content to create his own copy, or clone, of Jean Grey from blood samples he’d previously obtained. Unfortunately, the clone showed no signs of conscious life or mutant power (UNCANNY X-MEN #241).
Scott Summers lost his parents in a fateful plane crash that left his mother and father “dead,” and placed he and his younger brother Alex in an orphanage, the State Home for Foundlings, Sage, Nebraska. Scott remained there for a very long time, never adopted because, he assumed, of his bad medical reports conducted after the crash. His brother was grabbed very quickly, in contrast, and they were separated. At twelve years old, Scott was not a very happy boy.
After a fight on the playground between Toby Rails and Scott’s friend Nate, one in which Scott became involved, he was sent to the medical office where he met Doctor Robyn Hanover. They got to talking, and Scott told her his motivation for jumping into the brawl. He stood up for Nate, a fellow loner, but one that he didn’t even care for so much. “Something about him,” Scott said, “rubs me the wrong way.”
Scott was plagued by another of his common nightmares that night, dreaming of fire. He awoke screaming, so loud that the good doctor came running. She found him beside Nate, who comforted him, and insisted that Scott was fine, it was only a nightmare. Toby arrived on the scene as well, from his own dorm, to torment Scott further. He was sent away, and Scott was taken with Doctor Robyn. Once all was quiet, Nate disembarked on his façade, was revealed as Mister Sinister, and dealt with Toby, citing that while the boy once served his purposes, he’d now become counter-productive.
Chief Administrator Pearson approached the doctor and bidded she not take a special interest in Scott above the other foundlings, not play favorites. Doctor Robyn found him to be somehow upsetting. Regardless of the warning, she allowed Scott to help her move into her new office. They spoke again, about Scott’s headaches, and of his love of flying.
They were interrupted when Toby Rails was spotted atop the ledge of a nearby building. Scott scaled it automatically, intending to dissuade him from jumping. Below, Nate reprimanded Toby in front of the other foundlings. The doctor spoke with him, was given the cold shoulder, and wondered whether she’d come between he and Scott.
Atop the ledge, Toby seemed intent on departing the world, and despite Scott’s best efforts, the boy fell to his death.
After Scott had cooled off a bit, Robyn took him to the Sage Airforce Base to see a flight show. Robyn introduced him to her friend Rick and his wife. Rick Bogart was a pilot, and he extended care for Scott by inviting him to join him on a flight sometime. Scott was at first exhilarated, but he then declined in fear. Scott later met with Rick again at the base.
Rick proposed to his wife Trish that if they couldn’t pull together and find Scott’s family, they themselves should adopt him. Administrator Pearson, upon learning this, dissuaded it where he could. Robyn persisted until Pearson concluded that they’d let events play themselves out.
Mister Sinister abducted Robyn as he had Toby, conditioning her to become a woman devoid of emotion, an ice queen. She informed Scott that the Bogarts hadn’t pursued their application, and that it would be dropped. The Bogarts’ plane was sabotaged by Sinister, and the young couple were killed.
Scott was visited in a dream by Jean Grey and Professor Xavier, as a prelude to his being recruited to the Xavier School For Gifted Youngsters (X-MEN CLASSICS #s 41-42 from page 18 onward).
As for Alex; he was adopted straightaway by the Blandings family which had lost a boy themselves of Alex’s age, thirteen years. His new father invested emotions in him left over from his deceased son, Todd, and Alex was made starting quarterback on his dad’s football team against his will.
Alex was pulled aside by an upperclassman roustabout by the name of Vince, who could best be described as an envious boy prone to violent tendencies. His gang by his side, Vince threatened to do Alex in if he didn’t quit the football team and allow Vince to become the big man in town in Todd’s absence. Alex became queasy and stressed, surefire signs of his burgeoning mutant abilities taking stage.
Sinister, diguised in his human form as Nathaniel Essex, egged Vince on later that night, when he could speak to the boy alone. Sinister wanted Vincent to “stir the pot for [him].” Vince and his gang busted into Alex’s new home and kidnaped him. They took him and his adopted sister Haley to an abandoned factory on the other side of town.
Vince admited to having killed Todd. Alex had another spell. Haley turned on Vince with a vengeance for the life of her dead brother, and Vince shot her in the leg. Vince decided not to kill Alex, but to instead return to his home and kill his parents, taking all from the boy. Alex and Haley chased after him to his their house, and observed Vince preparing to plant a bullet in the place’s gas line. Alex begged him to stop, but that was nothing doing. His powers exploded forth from him to cremate Vince on the spot.
Sinister appeared to tell the baffled boy just what he was; a mutant, one “with the ability to absorb ambient cosmic rays into the cells of [his] body where [he] can transform and release it into super-heated waves of plasma energy.” Sinister placed a genetic lock on his powers, impeding their development, for he declared Alex the inferior of the two Summers brothers. Sinister buried the memories of the day’s events deep within Alex and Haley’s minds (X-FACTOR #-1).