Wu Zetian
Assassin of the Nightless City is an Assassin-class Servant able to be summoned by the Protagonist in the Grand Orders of Fate/Grand Order.
Assassin's True Name is Wu Zetian (武則天, Bu Zokuten?). Prioritizing the ease for understanding, she goes by the name "Wu Zetian". That is based on her posthumous name "Great Sacred Empress Zetian", which was given after her death. As for herself, she holds great liking to the title "Divine and Sacred Emperor", which she took upon claiming the throne.