Sinister
Real Name: Nathaniel Essex
Height: 6'3
Weight: 225 lbs.
Group Affiliation: Marauders
First Appearance: Uncanny X-Men 221, September 1987

Shrouded in mystery, little is known of the villain called Mr. Sinister, or simply Sinister. He has plagued Scott Summers (Cyclops) since boyhood, trying to manipulate him to his advantage because his optic blasts have proved to be the only force capable of doing Sinister harm. One would think Sinister would simply try to kill him...and yet, he has yet to make a serious attempt on Scott's life. Perhaps because his former master, Apocalypse, prevented him from doing so. Or perhaps it is simply the Summers genes which fascinate this evil scientist.

Mr. Sinister was the architect of one of the most brutal schemes ever to afflict mutantkind. Using the future X-Man Remy LeBeau (Gambit) to gather a band of vicious mutant killers, The Marauders, he set them loose to wipe out all mutant opposition, especially the X-Men. Then, he secretly cloned Jean Grey (Phoenix) to create the insane Madelyne Pryor, who nearly destroyed the team. But, Mr. Sinister ultimately lost his battle with the X-Men and, apparently, his life. Proving as hard to kill as any villain, he has returned to the fray, though his new scheme is as yet undetermined.