Ernst is the main villain of Ys VI: The Ark of Napishtim.
Ernst was a member of the Clan of Darkness, and a descendant of the people who stole the black sword Almarion, the control key to the Ark of Napishtim. His ancestors attempted to control the Ark, but failed and almost destroyed all of civilization before the Ark was sealed by the goddess Alma.
Seeking to succeed where his ancestors failed and claim the power of the Ark for himself, Ernst left the Clan of Darkness and joined the Romun Empire. However, his brother Geis followed him and became a mercenary, seeking to prevent his brother from causing a calamity. Ernst creates three faeries, Jue, Sera and Xisa, and sends them to the Canaan island to break the seal upon the Ark, in order to stop the Great Vortex which protected the islands from outsiders, while the Romun Fleet commanded by Admiral Agares awaited. Once the seal is undone, the Romun Fleet invades the islands and take over the village of Port Rimorge, while Ernst seeks to infiltrate the Ark. When the Romun forces kidnap the Rehdans, Ernst takes Isha along with him, as she had the power necessary to control the Ark, and destroys the stone remains of Alma, allowing him to bring the Ark of Napishtim from the depths of the sea and enter it.
Adol and Geis enter the Ark to stop Ernst and save Isha. Geis goes ahead of Adol but is easily defeated by Ernst. When Adol arrives, he draws the power from Isha and grows black wings, using Almarion to activate the Ark, challenging Adol. Adol defeats him and rescues Isha, but Ernst decides to draw more power from Almarion, against his brother's warnings. However, the sword explodes and severely injures Ernst, while the Ark goes haywire. Ernst apologizes and tells destroying the world was not his intention, so he tells Adol to stop the Ark and orders the faeries to go along with Geis before passing away.