One of Baelgard's four guardians, who is an artificial life-form made by Hiruda, using an ancient weapon as base. She is in fact Killrain's sister, Celestia, as Hiruda made her body as Xecty using Celestia's cells, but then she ended up getting infected by the darkness and Hiruda created a dark matter to absorb the forces of darkness, preventing her from further infection.

During a duel with Kiriya, an earthquake causes the two to fall into a cavern. Kiriya talks with Xecty and tells her the importance of hope and believing in your self, forming a close bond with her. Later, during the fight between Kiriya and Saionji, she gets in the middle and is stabbed by Saionji, sacrificing her life in order to stop the war. She explains to him that she did it in order to give hope to the world, and that Kiriya is her hope. Her spirit then joins the wind, as a way to protect both. She is later revived by one of the pods from the Sea Dragon King Ruins, and joins the Luminous Knights. She also becomes the priestess of Astraea's Tower of the Wind. Her soul blade is called Sword of Emperors Excelion (剣帝 エクセリオン, Kentei Ekuserion). She also contains Kiriya's Holy Grail, being drawn from her Kiriya's Ultimate Soul Blade (究極心剣, Kyūkyoku Shinken).

She seems to have some sort of bond with Elwyn.