Skull Queen

The Skull-Queen of Skral was one of Agatha Heterodyne's ancestresses with the help of Dagon Heterodyne after getting his attention with "200 warrior homunculi". How far back along the bloody family tree is not indicated.

The fact that her figure and costume weren't sufficient indicates some of the issues the family has.

There are no indications whatsoever as to where (or what) Skral was, except it was likely absorbed into House property.