黒い影

A mysterious being that prowls the streets of Fuyuki City at night, killing countless people. No one knows who or what it is and where it comes from.

After the end of the previous Grail War, her grandfather implanted a piece of the Grail into Sakura in an attempt to recreate it. This led to a remnant of the Third Holy Grail War, the eighth Servant Avenger, attempting to summon himself by controlling Sakura with an alternate persona, The Shadow.