Ernst Frederick Egin

Ernst Frederik Egin is an anime-original character, the father of Yuri Egin and grandfather of Rin and Yukio Okumura. Upon discovering his daughter was pregnant with Satan's children, Ernst ordered her execution, a decision he never reconsidered even after learning the full circumstances of her death.

Later possessed by Satan during the Blue Night, Ernst survived the possession but emerged with his hatred for demons dramatically deepened. As a member of the Grigori, he vocally opposed allowing Mephisto Pheles to remain within the True Cross Order, and worked to have Rin killed, believing his heritage made him irredeemably dangerous.

Convinced Yukio was fully human, Ernst recruited his own grandson to help him against Rin, ultimately attempting to sacrifice Rin to open the gate to Gehenna before Satan himself intervened. His zealotry and rigid worldview left him unable to see past his own convictions, even at the cost of his family.