Thread:Whovianfan/@comment-5616350-20160804020106/@comment-6945486-20160828160203

She is Sakura's darkside. Sakura gave in to her hatred and accepted she was a monster after Shinji Matou attempted to rape her. Sakura uses her dark powers to kill Shinji with a slash at his throat.

The Shadow is her servant. None of the spirits even Gilgamesh could have killed it. Saber and Hercules ended up corrupted by it. Only Rin Tohsaka with her secret weapon could fight through it.

http://legendsofthemultiuniverse.wikia.com/wiki/The_Shadow_(Fate/Stay_Night)