Golden Darkness a.k.a Yami-chan she's an alien :D To be مزید specific she was build on another planet سے طرف کی some scientists for assassination.Yes she is an assassin! Her original clothing is similar to Eve from Black Cat, She's actually based of Eve. That's why they alike!
Saber from the عملی حکمت fate/stay night and fate/zero. technically she looks like a normal human ,but don't be deceive ,she's actually a heroic Spirit that has the power to kill a normal human as if she's squishing a little insect.