Short answers, pulled from the story.
Necro was created by artist Akira Yasuda, known by his nickname Akiman, during the development of Street Fighter III: New Generation. Yasuda sculpted the character from a lump of paper clay which served as the primary reference for the sprite artists.
Necro was born as a young Russian man named Illia from a lakeside village before his DNA was altered by Gill's Illuminati to become a living bioweapon. He was tricked into serving the organization that promised him fame and fortune after the fall of the Soviet Union.
Necro stands 174 centimeters tall with a hunched posture and entirely white skin. His body is marked by red sun symbols on his shoulders and red lines extending from his head over his left eye and from his jaw over his right eye.
Lawrence Bayne took over the role of Necro in Street Fighter III: 3rd Strike after Michael X. Sommers voiced the character in the original New Generation release. The voice work helped to convey the personality of a misfit with a grudge and added layers to his relationship with Effie.
Necro did not belong in a Street Fighter game because his elastic limbs and long-range attacks put him at a significant disadvantage in the game's defensive nature. Critics noted that his fighting style felt like a collection of ideas that were not designed to work together.