Elyon Yesod is a character in the Dracul arc of the Sailor Moon musicals.
Nomenclature & Etymology
As with many of the other villains in the Dracul arc, the Death Nightmares' names were derived from Biblical and Kabbalistic sources. "Elyon" is one of the names of God in Judaism, and "Yesod" is one of the Sephiroth in the Tree of Life.
Elyon appeared for the only time in Pretty Soldier Sailor Moon ~ Last Dracul Final Chapter - The Seal of The Super Planet Death Vulcan. Unlike previous Death Nightmares, who were simple underlings of more important villains, Elyon Yesod and her fellow Nightmares were powerful spell casters and presented themselves to be strong enough to withstand even Sailor Planet Super Attack.
Their true allegiance was unclear in the musical, though their stated purpose was to destroy life on Earth. Count Dracul revealed that they were the ones responsible for the fact that Death Vulcan was so very powerful even though he was merely a torn-up planet. They also claimed to be the ones behind the entire conflict. In the end, they disappeared into the underworld, along with Dracul and his brother Dark Cain.