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Mother Marrow, is an old hag.
Her fingers are twiggy, her hair the color of smoke, and her nose is like the blade of a scythe. She also has clawed feet, like those of a bird of prey.
She is old and powerful enough that the air around her seems to crackle with the force of her magic.
The Wicked King
Her daughter and her attended Cardan‘s reveal, and presented him with fabric woven of spider silk and nightmares. The garment cut from it can turn a sharp blade, yet be as soft as a shadow against the skin. It turns out to be a trick. And if Cardan had accepted he would have found himself under a geas, allowing him to marry only a weaver of the cloth, which would have been Mother Marrow or her daughter. Cardan is blissfully unconcerned and asks Mother Marrow where her daughter is. Cardan tells the daughter that he would make a terrible husband, but asks her if she would like a dance. At this point, Mother Marrow drags her daughter away.
Mother Marrow is seen later in the book when Jude goes Mandrake Market. Mother Marrow offers for Jude to come and sit by her fire. She then offers Jude soap. She tells Jude that if she had not cost her daughter her dreams, Mother Marrow might actually like Jude. She then asks Jude why she came to the market and Jude replies that she came for a dress, she also tells mother Marrow that her daughter might have not liked “princess of the sea for a rival. Jude then buys a dress for her using pearl earrings from the undersea. Mother Marrow then gives Jude a walnut, Jude is hesitant to take it which makes mother Marrow ask “don’t you trust me, Girl?” to which Jude replies “Not as far as I can throw you,”. Mother Marrow tells Jude that she does not like her but she likes the sea folk less. Which Jude takes as her cue to leave.