The creature is the Dearg Due, a proto-vampire from old Irish legend. In the traditional story, she was a pretty girl who had a similar marriage mishap to what I have depicted in this story. She is reputed to be buried under Strongbow’s Tree in Wexford. The locals pile rocks on the spot to keep her in her grave. If she escapes from it, the legend says that she will go around attacking men in revenge for the cruelty she experienced in life.
I’ve tried to keep to that general scheme. The only reason she’s hunting for Maud is because Maud is special to Willie.