Euphrosynia Heterodyne

Euphrosynia Heterodyne was the daughter of Bludharst Heterodyne. A rare Heterodyne daughter, she was the love object of Andronicus Valois and thus part of the "fairy-tale" surrounding the Storm King.

We know next-to-nothing about her, and the little that we do know comes from the opera. Since she was, like Agatha is, a Heterodyne heir, she may well have been a Spark.