Reines El-Melloi Archisorte

→Go check out Lord El Melloi II Case Files.
…But it would be too much to leave it at just that. She is the legitimate successor of the El Melloi clan. She is Lord El Melloi II's younger stepsister. Her existence was hinted at in the El Melloi II entry of Character material which was published in 2006. In this series, she made a grand appearance along with her mercury maid Trimmau.
She only has a minor supporting role in this work, so her character was made a bit sweeter and childish than other works. Her hiding in a cardboard box and shouting “Boo!” with a hearty laugh is an excellent indication of this.
When her predecessor Kayneth went off in high spirits with his fiancée Sola-Ui to participate in the Holy Grail War and ended up magnificently having the table turned on him, Reines apparently had a dispute with the Sophia-Ri family, and she is still on bad terms with them even today.

Fate/Apocrypha material: Fate/Apocrypha Encylopedia