Justeaze Lizrich von Einzbern

Justeaze was the head of the Einzbern family two hundred years ago. Well acquainted with Zouken Matou, they had a dream of reaching a utopia that could eliminate and cure all hatred and suffering. Though they wished to exceed the limits of humanity by surpassing the body and reaching the soul, they were particular about reaching that state while still having human form. They were also acquainted with Nagato Tohsaka and Kischur Zelretch Schweinorg, considered a potential inheritor of the Jeweled Sword of Zelretch if not for Zelretch appraising the family as fundamentally evil.

Along with the family's then eight hundred year wish of retrieving their lost Third Magic, they sought to use the Holy Grail to reach that miracle. She was born to become the core of the Greater Grail, and she was the one to devise the ritual. Accompanied by Nagato and Zouken, who provided necessary land and starting materials for the ritual, and being watched over by Kischur Zelretch Schweinorg, she was sacrificed as the key to reenacting the ancient sorcery.

(Source: Type-moon Wiki)