Originally named Sion Eltnam Sokaris (シオン＝エルトナム＝ソカリス), Sion is an alchemist of Atlas located in Egypt, one of the three main branches of the Mage's 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. This is because in the earlier period she assisted the Church Organization on an assignment to demolish a vampire, but it was unsuccessful and everyone got slaughtered with the exception of her. This vampire, Night of Walachia, was the one who made her into one of his kind. She never returned to the Mage's Association from that day on and her pursuit had began. The effect wasn't as physically powerful, surprisingly she regained control of her body after the vicious attack. Now she feels a constant thirst for blood, and is searching for a cure before she becomes a vampire. She enters Tohno Shiki's town during her search for Arcueid Brunestud, hoping that she may know a cure for vampirism, to turn her back into a human once more. She is also seeking out the vampire Walachia to take revenge, who turned her into a vampire.
Sion is frequently composed and calculating, always determined for perfection. She is, in fact, moderately emotional and enormously easy to set off. She is a self-satisfied character, but whenever Shiki makes a remarkable statement, she gets displeased. Although she had lived most of her life in isolation, she gained her first true friend in Shiki.
Sion refined a special ability during her studies at the Atlas Institute: she can essentially "overclock" her brain, allowing her to forecast future events through mathematical calculation. She can also "split her brain" allowing her to run it in a parallel manner by separating her thought process, an ability dubbed "Memory Partition". She inherited the ability to "hack" other peoples minds with her "Ethelite" whip. In addition, if attached in the right way, this cord allows her to control other people's bodies. In her TATARI form, she can also use Ethelite to create a ''phantom''-like copy of an individual that is able to reproduce his/her abilities to an extent. Finally, she possess an unique Mystic Code called Barrel Replica, which is (as hinted by the name) a downgraded copy of the Conceptual Weapon Black Barrel.
- Birthday: 1 June
- Bloodtype: O
- Height: 161cm
- Weight: 48kg