Kingprotea

Alter Ego G, whose True Name is Kingprotea, is a High-Servant created by BB.

Fate/Extra CCC: Fox Tail

Initially, Kingprotea appears in the dream world of the trapped Hakuno Kishinami. She was trying to kill Hakuno by rampaging across Tsukumihara Academy but fails to accomplish her task.

Later on, Black BB orders Kingprotea to kill (eat) Hakuno, but after successfully eating him, Hakuno doesn't die and gets a chance to meet her inner form.

(Source: TYPE-MOON Wiki)