Killing is easy in the moral vacuum of videogames. So when Daniel Mullins needed a challenge, he gave peace a chance.

Mr. Mullins, 19, is the creator of "Felix the Peaceful Monk"—his character in a videogame called "The Elder Scrolls V: Skyrim." The game gives players wide latitude over their on-screen characters' appearance and actions. Felix, who is half man, half cat, has become a small-time Internet celebrity for his steadfast refusal to kill.

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