X was a stranger who came from the "mysterious dimension" called the Servant Universe. Seeking to accomplish her "true, dearest wish" to "defeat all Sabers", she brandished Secret-Calibur and left her home town, leaving behind an "expression full of bitterness."

Even before arriving at Chaldea, she managed to save an ancient royal dynasty from a crisis, settle the internal strife of the "Mankind Integration Union", and rout invaders from another universe, but such actions were trivial enough for her to not even remember accomplishing them. She will continue to brandish her sword until her goal is completed, and can still be seen "dashing across the sea of stars" even today. No matter what, she also plans to cut down the King of Heroes Gilgamesh

"It's sticking out...it's sticking out...it's really sticking out." X whispered as she saw herself in the reflection of a glass, her cap is used to hide her identity and ahoge, although it sticks out of the cap.

X sighed and simply let it be, putting her muffler once again to cover her lower face, she gripped the hilt of Secret Calibur and checked her attire,X's appearance is said to be of a young woman with "rough and sporty garments unseemly for Servants." Her blue muffler is a symbol of courage.

"Let's do this Arto....I-i mean X, got to remember my alias, no one has to know." X began her hunt for evil doers or any Rogue servant, specially alter sabers.