Mister Sinister is a fictional supervillain in the Marvel Comics universe, created by writer Chris Claremont and artist Marc Silvestri. He first appeared in The Uncanny X-Men #221 in 1987. Sinister, whose real name is Nathaniel Essex, is a geneticist with a deep obsession for mutant genetics, often manipulating DNA to create powerful beings. He is known for his pale skin, red eyes, and distinctive black and white costume. As a prominent enemy of the X-Men, Mister Sinister often collaborates with other villains and has a complex relationship with characters like Cyclops and Jean Grey. His ultimate goal is to create a superior mutant race, which leads him to engage in various schemes and conflicts throughout the X-Men storyline. Sinister's intelligence and powers make him a formidable foe in the Marvel universe.