Mr. Sinister was born Nathaniel Essex in London, England, circa 1859. He became a renowned biologist and contemporary of Charles Darwin. Obsessed with Darwin’s theories of evolution, he felt constrained by the morality in science and believed that experimentation outside the accepted norms was needed. His experiments became known as the Essex Factors in human genome. His dream was to bring about perfection in the evolution of humanity. This was driven by the loss of his own child, due to birth defects. His experiments ended up with Essex being thrown out of the Royal Society and discredited.
Essex then turned to a criminal element known as the Marauders who would kidnap the homeless and deliver them to Essex for his experimentation. He then ordered the group to awaken the immortal Egyptian mutant known as En Sabah Nur. The mutant who would be known to the modern world as Apocalypse. It was during this time that Essex’s wife, pregnant with their second child, became aware of what he was doing and threatened to leave him if he did not stop his experiments. Essex chose to abandon his wife and continue his work and ally himself with Nur.
The time traveling Cyclops and Jean Grey confront Nur and Essex and try to stop them. But they fail. In defeat, Jean Grey explains that to Essex that his actions will lead to the destruction of the world at Nur’s hands. Essex decides to quit and return to his wife who he finds dying after a premature birth. He begs forgiveness but she refuses, saying, “To me, you are…utterly…and contemptibly…sinister!” These are her final words to Essex. Alone he returns to Nur and creates a plague to kill the weak of the world. A culling.
Nur transforms Essex, giving him immortality and super strength as well as other mutant abilities. Nur demands that Essex leave his past life behind and begin another in his service. In doing so he must choose another name. Essex chooses as his name, his dead wife’s final words to him.
He calls himself, Mr. Sinister.
Throughout the X-Men and X-Factor comic line, Sinister has had an obsession with Scott Summers, something of a man crush. In all he does, he tries to keep Scott and his family safe while waging war on mutant and human alike. He cloned Jean Grey and created Madelyne Pryor from her for the sole purpose of breeding with Scott. This was successful and resulted in the birth of Nathan Summers. The futuristic mutant known as Cable. It is also revealed that he has influenced Scott’s life from the time when Summers was a child in an orphanage, taking on the persona of another of the children and befriending him. He later informs Scott of the release of the Legacy Virus, admitting that he cares to much for Scott to see him come to harm from the disease.
Sinister appears in the telling of many of the best X-Men tales of the early Chris Claremont era, Mutant Massacre and X-Cutioner’s Song, as well as Age of Apocalypse and The Further Adventures of Cyclops and Phoenix. He has been one of the most prevelant and powerful foes the X-Men have ever faced.