Ironically, Rei Ayanami is the most famous and mysterious character in the Neon Genesis Evangelion series.
Similar to how people are captivated by the unknown despite the fears that may accompany knowledge, her fans are lured to her air of mystery.
While there are certain truths that may be discovered regarding Rei's origins and fate at the end of the original series,
fans find themselves increasingly confused the more they investigate, as is the case with many things in the Evangelion series.
LCL, the primal matter of life containing Lilith's soul, and Yui, Shinji's mother and Gendo's ex-wife,'s genetic material generated Rei.