**Height:** 161 cm Originally named Sion Eltnam Sokaris, Sion is an alchemist of Atlas located in Egypt, one of the three main branches of the Mages Association. She is a genius scientist, given a position equal to the representative of ATLAS at an extremely young age. This event gave her the name of Atlasia, allowed to be used only by those who were the head of the Atlas. She is presently being chased both by the Church organization and Mage's Association. She enters Shiki Tohno's town during her search for Arcueid Brunestud, hoping that she may know a cure for vampirism.

Spoiler

In Tsukihime Worlds Sion takes the name "Atlasia" after becoming director of Atlas, while the Sion of Fate Worlds keeps her "Sokaris" surname. Within the World of Fate/stay night, she encounters Lord El-Melloi II during an expedition into the Library of Alexandria. Within the World of Fate/Grand Order, she supports Chaldea Security Organization in the Grand Orders, becoming the Master of Captain Nemo in the process.