Religion: Social Darwinist
Name: Mister Sinister
Alter Ego: Nathaniel Essex
Other Names: Sinister; Dr. Robert Windsor; Nosferatu; Pale Man; Edmond Atkinson; Arnold Bocklin; Mike Milbury; Dr. Nathan Milbury; Steven Shaffran; Lefty; Nathan Masters
First Appearance: The Uncanny X-Men (vol. 1) #221 (Sep. 1987): "Death by Drowning!"
Super? (Has Super Powers/Special Abilities/Technology): Yes
Number of Appearances: 255
Comic Book Appearances: 241
TV, Film Appearances: 12
Video Game, Computer Game Appearances: 2
Worked for: Weapon X
Mister Sinister masqueraded as a number of people who were influential in the life of Scott Summers (Cyclops) while the future mutant leader was growing up. Among these disguises were orphanage operator Dr. Nathan Milbury and bullies "Nathan Masters" and "Lefty." As Nathan and/or Lefty, Mister Sinister led a group that bullied Scott Summers in the orphanage he grew up in. The bullies Nathan and/Lefty who Scott Summers recalls in X-Factor (vol. 1) #34 (Nov. 1988) are apparently not independent characters but mere disguises of Mister Sinister.
Suggested links for further research about this character and the character's religious affiliation: