Mister Sinister

Mister Sinister (Nathaniel Essex) is a fictional supervillain appearing in American comic books published by Marvel Comics. Created by writer Chris Claremont, the character was first mentioned as the employer behind the team of assassins known as the Marauders in The Uncanny X-Men #212 (December 1986), then seen in silhouette in The Uncanny X-Men #213, with both issues serving as chapters of the 1986 "Mutant Massacre" crossover. Mr. Sinister then made his first full appearance in Uncanny X-Men #221 (September 1987), his appearance designed by artist Marc Silvestri.

A villain who usually prefers to act through agents and manipulation, Nathaniel Essex was originally a human scientist born in Victorian London who was inspired by the work of his contemporary Charles Darwin and became obsessed with engineering humanity into a new, perfect race of superhumans. As he learns about mutants (human beings born with the X-gene), Essex allies with the mutant villain Apocalypse, who uses alien technology to transform the British scientist into Mr. Sinister, an ageless being with super-powers. In the modern-day, he repeatedly clashes with the X-Men and related teams, while showing interest and a protective attitude towards the mutant heroes Cyclops and Jean Grey, believing their DNA can create the ultimate mutant. Sinister's body has been destroyed more than once, but he survives by commanding his body to repair itself or by transferring his mind into new host bodies and/or clones. Several co-existing Mr. Sinister clones (all with a copy of the original's memories and basic personality) later formed a community, with at least one clone having an X-gene (making him a mutant like the X-Men) and assuming leadership. This community was later destroyed, but one clone (apparently the one who carries the X-gene) survived and continues to operate to this day. Along with Cyclops and Jean Grey, he is often associated with the characters Apocalypse, Cable, and Madelyne Pryor, and is leader of the team of trackers and assassins known as the Marauders.

Making frequent appearances in the X-Men comics and related spin-off titles, Mr. Sinister has also featured in associated Marvel merchandise including animated television series, toys, trading cards, and video games. IGN's list of the "Top 100 Comic Book Villains of All Time" ranked Sinister as #29.

Backstory
Born in Milbury House in Victorian London, Nathaniel Essex was the son of Admiral Erasmus Essex and his wife Mary Essex. Earning a full scholarship to the University of Oxford, Essex becomes a biologist in 1859 and married his wife Rebecca. A contemporary of Charles Darwin, Essex becomes highly interested in theories and research regarding evolution and "survival of the fittest." He concludes that humanity is undergoing increasing mutation, due to what he calls "Essex Factors" in the human genome. After the loss of his four-year-old son Adam due to birth defects, Essex becomes more obsessed with his work. While he dreams of evolving the human race to a greater state of being, he is also frustrated that his peers do not agree with his methods due to moral constraints, arguing that science is beyond morality. His research methods and ideas lead to mockery and finally ousting from the Royal Society and the scientific community. Angry and bitter, Essex decides he will accept becoming a "monster" in the eyes of others if that is what is necessary to achieve success in his work.

Essex later hires the criminal Cootie Tremble and his gang, the Marauders. The Marauders kidnap homeless and neglected people off the streets of London as test subjects for Essex's experiments, including a man named Daniel Summers (an ancestor of the X-Man Scott Summers AKA Cyclops). Two years after Adam's death, the Marauders awaken the immortal Egyptian called En Sabah Nur ("The First One," known in later years as Apocalypse), whom Essex believes is the first of a new race of mutant humans. Holding similar beliefs regarding "survival of the fittest", the mutant villain Nur offers an alliance in order to aid Essex's research.

Cyclops and Phoenix, heroes from the future, arrive via time travel to stop Nur from conquering 19th century England, though they also hope to find a way to prevent Dr. Essex's future transformation into Mr. Sinister. Nur defeats Cyclops and Phoenix, leaving them for Essex to experiment on. Phoenix explains to Essex that continuing his work with Nur will lead to worldwide destruction. Sensing truth in her words, Essex decides to leave behind his research and dedicate his life to family instead, as his wife Rebecca is pregnant once again. Unknown to him, Rebecca Essex investigates his lab and is shocked to discover imprisoned human test subjects and the remains of their son being experimented on. Freeing the prisoners and reburying her son, the strain and stress evidently cause Rebecca to go into premature labor. When Nathaniel arrives to explain he is leaving behind his unorthodox research, he finds that the unborn child has died in stillbirth and Rebecca is now dying as well. Nathaniel asks for forgiveness, but Rebecca refuses, saying with her dying breath, "To me, you are... utterly… and contemptibly… sinister!" Following Rebecca's death, Essex allies with En Sabah Nur, becoming the villain's first "prelate." Using alien technology at his disposal, Apocalypse subjects Essex to a painful genetic transformation, turning him into an ageless being with chalk-white skin and gifting him with a form of telekinesis. When En Sabah Nur tells the transformed scientist to shed his past identity and choose another, Essex decides he will now be "Sinister." While claiming his humanity has now been carved out of him, Essex continues to carry Rebecca's photo until 1882.