Bludtharst Heterodyne is one of Agatha's ancestors, active roughly 200 years before the start of the comic. Along with his father Clemethious, he mounted one of the family's more aggressive and widespread assaults on Europan civilization, an effort which was bloodily opposed by the Storm King Andronicus Valois. His sibling was a rare Heterodyne female, Euphrosynia.

He is at least mentioned in Portentius Reichenbach's opera The Storm King, although it appears that the main villain of the piece is Euphrosynia's villainous fiance Ogglespoon.

In the rather fanciful tale that Klaus spins for Phil the Story-Teller, Bludtharst is replaced as Clemethious's son with The Goot Heterodyne.

According to the Castle Heterodyne fragment/mini-clank Agatha acquires in Paris, Bludtharst managed to corrupt the powers of Andronicus's mace The Platonic Solid; it is not made clear if this corruption is what led to the Storm King's transformation into a glowing undead berserker. A comment by the Master of Paris implies that Andronicus had done a complete about-face and allied himself with Bludtharst; Andronicus eventually says he and Bludtharst reached an unspecified personal "agreement".

However the two men's relationship ended, in Agatha H. and the Voice of the Castle, Agatha sees that Bludtharst's tomb under Mechanicsburg is inscribed with "He Couldn't Have Done It Without Me".