As a child, Nathaniel Essex traveled to Greenwich Park, South of the Thames, in London, and was amazed with the endless clean number of people, walking, what he believed to be, preordained paths for them. Essex believed that the sanctity and purity of it was heaven on Earth. He gained a full scholarship to Oxford University. Essex later became a biologist in 1859 Victorian England. He developed advanced theories on human evolution and was obsessed with Charles Darwin’s theory of evolution, though he felt Darwin and his contemporaries were shackled by too many moral constraints and that science was beyond morality. Dr. Essex dreamed of bringing the perfection of the evolution of the human race to the masses. After Dr. Essex's son, Adam Essex's, death at the age of four from numerous birth defects, including crooked bones and haemophilia, Dr. Essex was driven deeper into his work.
As member of London's Royal Society, Dr. Essex was regarded, by some, to be the greatest scientific mind of his generation, and, by others, as a dangerous man twisted by the obsession of his own research. An atheist, Dr. Essex believed in Darwin's theory of evolution and discovered that humanity was undergoing increasing mutation, due to what he called “Essex Factors” in the human genome. Dr. Essex also believed that, in the offspring of certain racially superior individuals, these parcels will, within a hundred years or so, mutate. Dr. Essex's theories were mocked, making him bitter, and his revealing of an unorthodox experiment resulted in his ousting from the Royal Society. Even Darwin himself suggested that Dr. Essex see a physician due to the trauma of losing his son. Angry, Dr. Essex stated to Darwin that if becoming a monster was what was required for science to progress, then he would become a monster.
After meeting Cootie Tremble, Dr. Essex was taken underground, where the Mauraders were collecting freaks, fools, and all types of misshapen folk off the streets of London. Dr. Essex hired the thugs to continue their work, so he could perform experiments on the victims in the name of science. After awaking, the immortal mutant, En Sabah Nur, ordered the Marauders to take him to Dr. Essex and the time-travellers, Cyclops and Phoenix, arrived, believing that they were to prevent Dr. Essex’s future transformation into Mr. Sinister, but unaware that Madame Sanctity of the Clan Askani had sent them to the past to stop Nur from conquering England. As Mr. Sinister, Dr. Essex was necessary for the birth of Nathan Dayspring, the Askani'son, who Madame Sanctity worshipped. Dr. Essex even went so far as to dig up his dead son and experiment on him. Growing more curious of her husband's work, Rebecca Essex checked in Dr. Essex's lab, to find the body of their son in an incubation tube. After digging-up Adam's grave to prove her suspicions, Rebecca passed-out, from the shock of finding the coffin empty, and Nur approached Dr. Essex, stating that he was interested in his work.
Left with the choice of continuing his work or his wife shunning him, Dr. Essex allied himself with Nur. Dr. Essex explained to Nur that he was the first born in, what Dr. Essex believed, would be a great mutation in the human race. After taking Nur to the Hellfire Club, Nur demonstrated his power before the men and explained that Dr. Essex's theories of mutation were more near than he believed. After defeating Cyclops and Phoenix, Nur left them to Dr. Essex, as test subjects, and Phoenix explained to him that if he accepted Nur's offer, the world would be destroyed. Deciding to leave his life of unorthodox science and dedicate his life to his wife and unborn child, Dr. Essex returned home, to learn that his wife had freed all of his captives, prematurely had the baby, and was dying of stress. Asking for forgiveness at her side, Rebecca denied him and stated, "To me, you are... utterly… and contemptibly… sinister!", with her dying words. Dr. Essex agreed to Nur's offer and was ordered to create a plague to destroy the weak of the world, as Nur's first prelate. Apocalypse painfully transformed Dr. Essex into an ageless being of extraordinary pallor, with telekinesis in his Alien Ship, asking him to shed his past name and choose another. With his new abilities and dispassionate outlook, Dr. Essex took the new name, "Sinister", Rebecca's last words to him.
Emerging from Nur's machines, Mr. Sinister stated that he willingly allowed whatever humanity he had to be carved out of him, all for the sake of science. Cyclops escaped and began to fire his optic blasts intensely at Mr. Sinister, prompting Sinister to question what he did to make Cyclops hate him so much, realizing that Cyclops held hidden knowledge. After escaping, Mr. Sinister returned and killed Cootie, who Phoenix was attempting to telepathically ease his dying pain, stating that her supposed kindness caused more suffering than any tyrant and one must be willing to be cruel to search for the truth. Cyclops pleaded with Sinister not to create the plague and Sinister realized, with the ease that Cyclops spoke his name, that he had met him prior, starting an obsession to dissect Cyclops or any of his bloodline. After the time-traveling duo defeated Nur and began to shift back to their own time, Mr. Sinister appeared and stated to Cyclops that he was sure they would meet again. Returning to Nur's Ship, Nur demanded to know why the plague was not complete and Mr. Sinister stated that he manipulated the plague, so that it would affect only Nur himself, but his immune system quickly adapted to it. Nur asked why and Mr. Sinister replied that cruelty for no purpose was ignorance and ignorance was the greatest enemy of science. As Nur began to return to his hibernation, he stated that Sinister's defiance was a sign of his strength, but it would not be tolerated again. Nur warned Sinister to never forget who has the true power and, when he returns, it will be the dawn of the Age of Apocalypse and Sinister will be his servant.
In 1882, Sinister was present at Darwin's funeral, reveling in the irony that the man who was once vilified was being buried in Westminster Abbey, the highest church of England. As he walked away, Sinister mused why he kept a small box containing a picture of his wife if he truly left his humanity behind. He discarded the box, reminding himself that Essex, his wife and his children were dead. Soon after, Sinister left for the United States.
Still obsessed with the Summers' bloodline, Sinister operated an obstetrics clinic, Essex Clinic, in New York, in the late 19th century, and performed side research on society's deviants. Renamed Nathan Milbury (an alias based off the name of the manor of his former wife), Sinister had unrestricted access to an abundance of generational genetic material to study, including that of the adult Daniel Summers, the first Summers in America and a former victim of his experiments in London, and his wife, Amanda Mueller.
Search for the Perfect Mutant
Feeling threatened by the power of Nur, Sinister conducted numerous experiments in his time, searching for a powerful mutant to oppose his master and the means to improve himself. For a time, Sinister continued to advance his master plan to serve Nur (and his own ends), but in general preferred to let bloodlines breed naturally (rather than hastily transforming them), in order to produce the most racially-supreme beings.
In 1891, Sinister came across another pair of time travelling mutants from the future, the X-Man Gambit and a shape changer called Courier. Gambit traveled to New York to find Sinister before the Thieves Guild could on the orders of Candra, who hoped to learn about Apocalypse from Sinister himself. In exchange for the lives of the Thieves' Guild members who got caught by Sinister, Gambit traded in a sample from Courier to Sinister in exchange for the information which was given to the now freed Guild's members who went off to find Apocalypse's hidden sanctuary protected by Ozymandias. Sinister and Gambit followed in order to stop Candra and on Gambit's part to save the Thieves' Guild. Afterwards Sinister erased the memories of the Guild members of Apocalypse's hide out and implanted these memories into Gambit's subconscious when he noticed Gambit had previous surgery in which Sinister recognized the technique as his own. Sinister disappeared soon afterwards leaving Gambit and Courier to fend for themselves.
In 1899 in England, Sinister helped awaken Apocalypse from his slumber. Apocalypse thanks him for his servitude over the years and says that out of all the servants, Sinister is the most loyal. He offers Sinister a reward but Sinister bitterly refuses stating he "No my lord, I exist to serve you, and you alone". Sinister has a scowl on his face as he says this showing obvious contempt for his position. Later that same year Sinister successfully infects Apocalypse with his new techno-organic virus bred at Apocalypse's behest. Unfortunately for Sinister Apocalypse's ability for his molecular structure to adapt is able to fight the virus and is only weakened by it. He threatens Sinister if they were to ever meet again, Apocalypse would kill him. Sinister flees while he can. This partially drove his desire to find and create a powerful mutant in order to defeat Apocalypse later on.
20th and 21st Centuries
In 1907, Mr Sinister surfaced in Canada on the hunt of a clawed wild man "Logan". He sent his Marauders to hunt him down to learn his secret: he was a mutant.
World War I
In 1915, Sinister went back to England and granted Jacob Shaw the ability to shape-shift, which he used to murder his brother, Esau Shaw. What Sinister hoped to obtain from aiding Jacob Shaw remains a mystery.
In the 1920s, Sinister encountered and influenced the work of a man named Herbert Edgar Wyndham, who dreamed of doing what Sinister had already accomplished—breaking the genetic code for human DNA. During a trip to an international conference on genetics in Geneva, Switzerland, Wyndham suddenly felt ill. Stumbling out into the street Wyndham met the hypnotic gaze of a man in a top hat and coat, shrouded in darkness. From this stranger, Wyndham was handed a gift that should not have existed in that time—a blueprint for breaking the genetic code. Whether Wyndham's benefactor was Sinister or not remained unrevealed.
In the 1930's, Sinister spent some time in California, gathering subjects for his experiments; while in Los Angeles, he met and became interested with radio comedienne, Faye Livingstone. Discovering his secret laboratory one night, Sinister confronted Faye with the truth, that she carried the x-factor in her genes and her offspring would produce special children, children that would be more than human. Horrified, Faye tried to leave, but Sinister kept her prisoner. Months passed, filled with degrading examinations, and affected pity gave way to foul contempt, until Sinister broke Faye in mind and spirit. Sinister made Faye (not let her) see behind the illusion that was Nathan Essex. Then, in the middle of a raging storm one night, Essex flung the door open and released her, without speaking or gesturing. In time, Faye was brought to the Carlysle Nursing Home in San Diego, California, with her mind and body failing to cancer. Due to her love for Essex, Livingstone had never married or had children. The offspring Sinister so eagerly anticipated never came to exist. Once a year, a "Mister Essex" would come and visit her, though he would never admit to anyone (not even himself) why.
World War II
In 1944, as a Nazi scientist, Sinister worked along with geneticist Josef Mengele, earning the nickname "Nosferatu" from the captive children at Auschwitz. One of his characteristic was he liked to play a piece of Franz Schubert. Due both to his pale visage (believed to be albinism), Sinister frightened even the Nazis, often giving children candy in exchange for their blood as a means of bribery. Young Max Eisenhardt witnessed Nosferatu's actions.
"Nosferatu" roamed the camp and picked people at random, looking for mutants for experimentation in his quest to catalyze the mutator gene. He could even pick those heading to the gas chambers, without interference of the guards who were terrified of him.
Those he picked were never seen again, and it was believed by some that he was a hero, helping people to escape.
Max Eisenhardt didn't trusted him, and consequently became a Sonderkommando to avoid selection. Cleaning out the furnaces of the crematoria, he discovered the bodies of his friends who had been picked, turned into monsters.
Later Sinister created Experiment N2, a clone of Namor the Sub-Mariner, which could forcibly suck the water out of Namor and use it to douse the android Human Torch's flames. To Sinister's considerable surprise, though, Captain America was able to defeat N2. It was during this period, in 1944, that Sinister came across a man named John Greycrow, who would become Scalphunter, his first "new" Marauder.
After the war, Max Eisenhardt became a Nazi hunter, in order to find "Nosferatu", in vain. Each time he heard the piece of Schubert (such as the time Dark Beast attacked the Genoshan Excalibur and listened to it while experimenting on Karima Shapandar), it made Max (now known as Erik and Magneto) wonder if it is the time he will find "Nosferatu".
In 1946, a Dr. Nathan Milbury was involved with Project: Black Womb, a secret government project headed by Amanda Mueller and aided by Dr. Alexander Ryking, Dr. Kurt Marko, and Irene Adler, which studied, but did not alter, thousands of children, mostly mutants, in post-natal holding tanks. Dr. Brian Xavier was a colleague of Dr. Ryking and Dr. Marko at the project, which was based in Alamogordo, New Mexico, but whether he was involved with Project: Black Womb remains unclear.
Teaching at Oxford
He worked as a lecturer at Oxford University teaching Genetics and Biophysics. Two of his students were Charles Xavier and Moira Kinross. It had also been hinted that Essex interfered with Moira and Xavier's relationship. Charles was suspicious of his new professor as he could not read his mind.
In 1968, Sinister was present in Vietnam, where he and the ever-loyal Scalphunter kidnapped both soldiers and villagers to perform experiments on, giving Sinister the alias White Devil. Victor Creed was hired to investigate the disappearances, but his employer was beheaded by Scalphunter, who gave Creed a large sum of money to buy him off and recruit him as one of Sinister's "enforcers".
State Home for Foundlings
For decades, Sinister secretly observed the development of mutant children, as they grew (many of which had been “earmarked” by Project: Black Womb) in the State Home for Foundlings in Omaha, Nebraska. Creating a cutting-edge laboratory underneath the Orphanage, which seemed to have some quasi-biological properties, Sinister cruelly manipulated the children's childhood developmental processes and even tried to control their adult lives, so they might become his minions. Another notable test subject was Emma Frost, who Sinister had admitted to his Essex Clinic. After years of perfecting his own body, studying the Summers' bloodline, and manipulating others, Sinister had become a megalomaniac, but still quietly feared the wrath of Apocalypse.
One evening, while in his laboratory, Sinister registered the same optic blast that Cyclops had fired a century ago and, learning that he was recently orphaned, began the process of studying the young Scott Summers. After surviving a plane crash, Scott and his younger brother, Alex Summers were hospitalized for injuries sustained during their landing. Scott and Alex, both, suffered traumatic amnesia regarding the plane incident. Alex left the hospital after two weeks, but Scott remained in the hospital for a year, where Sinister began experimentation on him for a year. At one time, Scott awoke from his injuries and destroyed the roof of the hospital, at which time, Sinister began creation of ruby-quartz lenses for the youth to function in society. Upon recovering, Scott was placed in the State Home for Foundlings and was subjected to batteries of tests and experiments by Sinister. Sinister, also, placed mental blocks on Scott and took-on the role of Nate, aka "Lefty", who was Scott's roommate and would bully him at the orphanage. Sinister arranged for Alex to be adopted, while keeping an eye on him, while Scott remained. After allowing Scott to be adopted, by Jack Winters, a mutant criminal known as the Jack O'Diamonds, Scott began to suffer from severe headaches and was sent to a specialist, Sinister, who provided him with lenses made of ruby-quartz.
Sinister lost control over Scott, after a display of Scott's power had attracted the attention of the mutant telepath, Professor Charles Xavier, who teamed up with FBI agent, Fred Duncan, in their mutual attempt to find Scott. Scott was rescued from Winters' clutches and was enlisted by Professor Xavier as the first member of the X-Men, a team of young mutants who trained to use their powers in Professor Xavier's dream for human/mutant equality, and second student to enlist in Xavier's School for Gifted Youngsters, to become Cyclops. Sinister continued to monitor Scott, even becoming a long-time neighbor of his grandparents. At some point, Sinister spliced mutant genes from Alex, into Ahmet Abdol, who became the Living Monolith, able to absorb cosmic energies and use them to grow to enormous size.
At one point, learning through underworld contacts, Remy LeBeau approached Sinister, who Sinister immediately recognized as a younger Gambit, for help in controlling his powers. Sinister reversed the surgery that he performed years earlier and removed some of Remy's brain tissue, to reduce his power levels and afford him a greater degree of control. It is possible that Sinister agreed to help him in order to insure the series of events that lead to Gambit (and Courier) going back in time, which allowed Sinister to gain Courier’s powers. As a result, Remy was now in the geneticist's debt.
Years ago Mr. Sinister hired Kraven the Hunter to obtain a DNA sample from the original X-Men. Mr. Sinister, using the DNA of Kraven the Hunter, the original X-Men and the sample of the Carnage Symbiote created Xraven, but left him in his tank to use him for another time.
The Perfect Mutant
Sinister eventually realized Scott and Jean Grey's mingled genes would create a mutant of unparalleled power, to destroy Apocalypse and thus free him from the yoke of that ancient tyrant. Around this time, Jean, actually the Phoenix Force, was acting reckless, so Sinister created a clone of her. Sinister's plot was to produce a child from the union of the clone and Scott, whom he believed would become a genetically superior mutant. To Sinister's disappointment, the clone had no life and did not develop any mutant abilities at puberty, as he had hoped. Sinister left the clone in her incubation tube, under the orphanage, as a failed experiment.
Birth of Cable
It was at the moment of the Dark Phoenix's death that a spark of the Phoenix Force was accidentally bestowed on the clone and renewed Sinister's interest. Sinister named the clone Madelyne Pryor, as a pun on her "prior existence" as a cell sample taken from Jean, and arranged a set of false memories for her. Mister Sinister played a part as matchmaker, by giving Madelyne a personality he knew Scott would like and placing her where they were sure to meet, as a pilot for his grandparents. Madelyne met Scott in Alaska and the pair eventually wed, giving birth to Nathan Christopher Charles Summers, Nathan from an implanted suggestion by Mister Sinister in Madelyne. Young Nathan Summers was so powerful that, upon his birth, he woke Apocalypse from his hibernation. After losing a battle of leadership to Storm, Madelyne convinced Scott to move with her back to Alaska and live out their lives there, a subconscious suggestion implanted by Sinister—the remote location made it easier for him to study and if need be abduct the child.
After learning of the existence of the Morlocks, Sinister recognized that someone, Dark Beast, had been perverting his own "signature" in genetic experiments, unaware that Dark Beast was the student of an alternate reality version of Sinister, and, to prevent further unauthorized usage of his theories, orchestrated the massacre of all of them. Sinister ordered Gambit to assemble a new group of Marauders, Scalphunter and Sabretooth, with new members, Arclight, Blockbuster, Harpoon, Prism, Riptide, Scrambler, and Vertigo. Sinister also gained genetic samples from all of the members. Remy did not realize that Sinister would employ the Marauders to massacre the underground mutant community and, seeing the horrific results of his actions, Remy attempted to stop the massacre, but was almost killed by Sabretooth and fled. Gambit did this, and many other tasks, for Sinister to repay his debt. Sinister's massacre was almost a complete success, but stopped short, by the X-Men, X-Factor, and Thor, which resulted in the deaths of many of his Marauders. Though some of his Marauders died during the Massacre, Sinister’s mastery of genetics and cloning technology enabled him to recreate his Marauders again and again.
After the unexpected return of Jean, Sinister aimed to eliminate Madelyne before the truth of her creation was revealed, and sent his Marauders to kill her and kidnap her son. Maddie was hired, by Sinister, to fly a cargo to San Francisco for a large sum of money and, at the last minute, decided to take Christopher with her. Maddie used her latent psychic powers to defend herself, but lost baby Christopher to her enemies. Maddie was shot multiple times and left for dead, then taken to a hospital in San Francisco, as a "Jane Doe". Sinister took Nathan to his secret lab hidden under the orphanage, where he experimented on Nathan for months. Sinister was thorough and erased all existence of Nathan and Madelyne. Scott, later, attempted to reconcile with his family, but there was no existence of them except a baby toy in their old home.
While Nathan was Sinister's victim, Cyclops was informed of his whereabouts and attempted to rescue him, but demons escaped with baby Nathan, instead. While investigating Nathan's disappearance, N'Astirh appeared and took Madelyne to the orphanage basement, revealing Sinister's laboratory and an incubation tube with her name on it. In the lab, Mr. Sinister revealed himself and bound Madelyne, explaining her existence as Jean's clone to her. After being told that he would experiment on her, Madelyne used her considerable power to break free of Mr. Sinister's bonds and N'Astirh presented her with her son. As the Goblin Queen, Madelyne descended into madness after Sinister revealed she was only a tool modelled after Grey and returned to New York, where she battled X-Factor and the X-Men, blaming Jean and Scott for the misery in her life.
After Madelyne's death, Jean began to scream in pain and Storm ordered Psylocke to take Scott and the X-Men into her mind, where Mr. Sinister was attempting to erase all of Jean's memories, until Jean defeated him on the Astral Plane.Following Mr. Sinister's psychic trail, Marvel Girl tracked him to the School for Gifted Youngsters and X-Factor and the X-Men were ambushed by the Marauders. While interrogating Malice/Polaris, Mr. Sinister destroyed the school. Scott, soon, learned that Mister Sinister ran the orphanage in which he was raised, provided the ruby-quartz lenses, and the truth about Madelyne's creation, while Sinister mentally locked-off access to Scott's optic blast and attempted to claim Jean. While X-Factor and the X-Men battled Sinister and Malice, Scott was bound. With Alex bombarding Scott with his plasma blasts and verbally agitating him, Scott seemingly killed Sinister with an unchecked optic blast.
Before Sinister could reclaim young Nathan, however, Apocalypse infected Nathan with a Techno-Organic Virus, which would start a time paradox that ensured his own creation. The virus threatened to consume baby Nathan, until a member of the Clan Askani, Sister Askani, appeared from the late 37th-early 39th century to Cyclops, claiming that Nathan would become a savior in their time and that the Clan would cure him of the virus. Choosing to save his son's life and believing that he would never see him again, Cyclops agreed and Nathan was taken into an alternate future ruled by Apocalypse.
Later, a group of mutants known as the Nasty Boys appeared, working alongside an evil duplicate of James Madrox. The evil Madrox wished to kill the true Madrox to ensure his continued independence and sought Sinister’s help in doing so; he sent the Nasty Boys to aid Evil Madrox by fighting X-Factor. Eventually, the Evil Madrox was re-absorbed by the original Madrox, and subsumed into him.
Meanwhile, Quicksilver's powers were being secretly overcharged by Senator Steven Shaffran, who was trying to discredit X-Factor in order to spur on his political career. Unknown to Shaffran, though, Sinister took the senator's appearance and revealed Shaffran's deeds to the team. Shaffram later confronted Sinister, and planned to kill him, but only succeeded in killing himself when his bullet ricocheted off of Sinister's armor. Later, Sinister sent his Nasty Boys to track down a rogue Malice, who was trying to break free of Sinister.
In an earlier confrontation with X-Factor, Malice had possessed Polaris, but Polaris’s powers prevented the possessing entity from departing Lorna Dane’s body—something Sinister knew would happen. Malice did eventually break out of Dane’s body, and was determined to escape Sinister’s control—for a being used to existence as an incorporeal energy being, entrapment in a physical body, even one as powerful as Polaris’s, was Hell for her. A massive fracas between Sinister and the Nasty Boys, Malice, and Havok and Polaris broke out. Both Alex and Lorna tried to absorb Malice (in order to prevent the other from being possessed), but the strain wound up fatally disrupting Malice’s energy form (as planned by Sinister). Seeing as the conflict had no meaning anymore, Sinister and his minions withdrew.
Sinister unwittingly unleashed the Legacy Virus upon the Earth, a plague engineered by Stryfe, a clone of Cable. Sinister revealed to Cyclops Stryfe's trick, and mentioned Cyclops' "brothers", something Cyclops picked up.
Genesis forced Sinister to confront both Faye and himself about the relationship, but Sinister refused, adamantly maintaining that she was nothing more than a useless husk to him. After sharing a telepathic dance with Essex, Faye died in his arms.
In parallel, Sinister hired Siena Blaze on Muir Island for to stole DNA's Proteus, Moira MacTaggert defunt son. Although Blaze lost her mission, confronted by Rachel Summers, she arrive to scratch her. Initially angry by Blaze's failure, he changes his mind when Siena tell him on her confrontation with Rachel and recolt Phoenix II's DNA from her fingers.
Sinister later took in the mutant Threnody, and used her unique powers to track down victims of the Legacy Virus, which he could then study and work on to develop a cure. Moira MacTaggart, long-time ally to the X-Men and one of the top genetic immunologists on the planet, eventually developed a cure for the Virus. This cure was released thanks to the sacrifice of the mutant Colossus. Sinister offered to clone him to his fellow X-Men as a form of gratitude (though he may have had ulterior motives), but they refused.
Sinister battled with Gambit in Seattle as he searched for Rogue
Sinister considered a similar course of action for the Genoshan Mutates, who were created by the Sugar-Man using the same alternate reality Sinister's technology as well, but decided against it, because the process had turned the mutates infertile. Consequently, Sinister did not consider them a contamination of his work.
Age Of Apocalypse
After the creation and collapse. Mr Sinister had to deal with the aftermath and the survivors of the alternate reality Age Of Apocalypse. He battled one of his alternate reality counterpart's creation: X-Man (Nate Grey).
Death of Apocalypse
Fortunately for Sinister, Cable also had a deep grudge against Apocalypse, and when Apocalypse merged with Cyclops at the climax of The Twelve gathering, Cable and Jean Grey tracked the merged being back to Apocalypse's birthplace of Egypt. Jean separated Apocalypse's astral form from Cyclops' body, and Cable sundered the freed spirit, fulfilling his destiny as written by Sinister. This gave Sinister the freedom he'd long sought, as Apocalypse had always kept him on a tight leash.
It was revealed that Mr Sinister had involvement in the Weapon X Project as Dr. Robert Windsor,  Sinister supposedly helped a number of prisoners escape from Weapon X's concentration camp Neverland. However, Sinister merely took these mutants to his personal labs to perform experiments on them. At the same time, Sinister created a group of super-powered beings called The Children, which he was forced to give up to John Sublime, after Sabretooth killed the first of the Children: Hans.
When the High Evolutionary activated a satellite that stripped all Homo superior of their mutations. Essex, who had come to support his student's work, revealed himself as Sinister and modified the beam to mutate every human on Earth, hoping to create an entire planet of lab subjects. Soon after, the mysterious Neo attacked many of Sinister's facilities.
Rasputin Blood Line
As recently revealed, Sinister also had a history with the 'mad monk' Grigory Rasputin. He has been tracking his descendants as the 'Pale Man', most notably Mikhail Rasputin and Colossus). 
He paired with Mikhail to kill off all of his living relatives to allow the essence of Grigory Rasputin to be concentrated in one host and become reincarnate. After the brothers fought Sinister’s influence, it was discovered that the reason he wanted Grigory in power was to stabilize his own failing abilities. Sinister admitted that he was weakened—being unable to shapeshift or teleport and actually sustaining injuries from Colossus' attack—but vowed vengeance for when he did have his abilities restored.
House of M
Mister Sinister's had a small, yet significant, presence in the divergent House of M reality. While remaining a physiologically altered geneticist, this Sinister was a quite genteel, friendly person—even to the point of offering the visiting trio of Deadpool, Cannonball and Siryn a (drugged) barbecue dinner. Sinister was apparently rejected from society for experimenting on mutants, which was taboo under Magneto's rule, and lived on a secluded Nebraska farm. Despite the difference in personality, this Sinister was also responsible for the birth of an infant Cable, who Sinister believed was a potential savior for the world of the House of M.
The Scarlet Witch returned the world to normal but with the Mutant population greatly reduced. Also unknown was how his 100 years of genetic sampling reacted to the effects of the Decimation. Sinister enhanced himself with mutant DNA samples, which could have been affected by the Scarlet Witch "no more mutants" decree.
Sinister returned, and convinced Gambit and Sunfire to join his Marauders, consisting of members old and new, in exchange for helping them overcome their conditioning as Horsemen of Apocalypse. After a battle between the Marauders vs. Cannonball and Iceman he was disgusted at how the Marauders were almost getting beat, and he left Guthrie's mind in a blank state as a threat to the X-Men.
Desperate for any solution, Beast even went to the extreme of begging assistance from the super-villain scientific community, including Sinister.
Now an endangered species the mutants began inviting. This led to a fight between the Marauders and the surviving X-Men.
After the birth of the first mutant child since M-Day, Mr. Sinister and his Marauders were among the factions that moved to capture her. They succeeded, and the child fell into his possession, but he was betrayed by Gambit and Mystique, who killed him in order to use the child to cure Rogue.
However, Sinister had long since made arrangements in case of his death, and after his death, one of his contingency plans activated, which if successful, would allow him to transfer his consciousness into Professor X, Juggernaut or Sebastian Shaw, three candidates he had prepared since their childhood.
Unforeseen complications arose however, in the form of Juggernaut being immune to the transfer process due to the properties of his magical helmet, and Black Womb attempting to usurp the process in order to gain Sinister's essence and powers for her own devices.Both her and Sinister's plans were foiled when Sebastian Shaw and Gambit destroyed the machinery. Sinister briefly managed to seize the body of Xavier, but was driven out and thought to be destroyed.
Mr. Sinister gave a eulogy for some of the deceased X-Men.
However, it was revealed later that Claudine Renko was drawn to a machine that implanted Sinister's essence in her, transforming her into Miss Sinister. Sinister began steadily gaining control of her, and in order to escape his possession she attempted to transfer her own consciousness into X-23. This was revealed to have been Sinister's plan all along, since he wished to possess the body of a mutant with a healing factor. The plot failed however, and X-23 drove him out, with help from Sinister's long time adversary Gambit. Sinister instead possessed a clone, and promised to "take care of" the injured Miss Sinister.
Sinister World Fair
Later, he returned to San Francisco, and using the head of the Dreaming Celestial, Sinister transformed a section of the city into an all-Sinister zone, a sort of hive-mind of Sinisters, declaring that he had succeeded in creating a species greater than Homo superior.Meanwhile, Cyclops was alerted of an incoming threat by Agent Brand; the Celestials were coming to Earth. Sinister offered a ceasefire for a conversation, despite knowing that the X-Men had planned a trap for him. Sinister revealed his plans and seized control of the Extinction Team's minds, but failed to control Emma Frost whose diamond form prevented telepathic intrusion. This allowed Hope Summers to shoot Sinister in the head seemingly killing him. Another of the Sinisters merely assumed the role of leadership, declaring that the X-Men could not kill him since he was no longer an individual, but a system.
The X-Men continued fighting Sinister's clones, with the primary consciousness simply transferring from one body to another. In the heat of battle, Sinister let slip that he based his new self on Cyclops' brain patterns, which prompted Emma Frost to telepathically invade and destroy his mind, since her great familiarity and experience with Cyclops' brain gave her easy access.As soon as the first iteration of Sinister's new species was destroyed however, a new version emerged from his machine, immune to Emma Frost's telepathic intrusions. He declared that his machines had been set to analyse the data gathered by his last iteration, prompting his new self to be created without overt reliance on Cyclops' brain patterns. He stole the Museum of Fine Arts before committing suicide, since a new version would merely sprout from the machine.
Sinister returned to one of his old labs and activated a self-destruction device which allowed a Phalanx he captured long ago to escape and destroy a whole town before being destroyed.
Avengers vs. X-Men
Sinister then hid underground and created a replica of 19th century London in the Moloid Caverns. Here, Sinister ruled the city which was populated by his clones and reinforced by advanced technologies. Sinister planned to capture the Phoenix Force in order to use it for his own purposes. He lured the Phoenix Five down to his underground city and after weakening and capturing them through use of advanced technology, partly based on clones of X-Men and Marauders, used a device to siphon the Phoenix into 6 clones of Madelyne Pryor. Emma Frost, one of the Phoenix Five enters the mind of one of the Madelyne's and communicates with the Phoenix, managing to convince it that Sinister only means to keep it trapped forever and reminding it that it had a purpose for coming to Earth in the first place. The Phoenix leaves the clones and returns to the Phoenix Five who incinerate Sinister, all of his clones and destroy his city.
Sinister was revealed to have survived the Phoenixes purge by replacing Cyclops' head of PR with himself, remaining dormant in her mind until after the Phoenix had left Earth, after which he seized control of her body and eradicated her consciousness. After Cyclops lost the Phoenix Force, he was imprisoned by the Avengers and Sinister visited him in jail, telling him that only he could stop him and daring him to either stay in jail as a political prisoner or break out and take him on before vanishing. Cyclops vows that it isn't over.
With the release of a the Terrigen Mist in the atmosphere of the Earth, it was discovered this subtance was incredibly toxic for mutants. Mr. Sinister began experimenting on unwilling subjects, trying to make Inhuman and Mutant DNA co-exist in order to allow the creation of a genetically superior species of mutants.
Sinister caught the attention of the X-Men after the disappearance of Colossus and Magik at the hands of the Marauders. When Sinister was confronted by the group of mutants, he deployed his only successful speciment, a clone of the recently deceased Cyclops. Most of the X-Men tried to contain the clone as it went to the surface and began to wreak havoc, and Colossus remained underground fighting Mr. Sinister. The clone ultimately exploded due to its inestability, and Mr. Sinister was subdued by Magik. The X-Men would later arrange with S.H.I.E.L.D. the detention of Mr. Sinister and the Marauders.