The Sword of Maiden's Tears(1994)
(The first book in the Twelve Treasures series)
A novel by Rosemary Edghill
Stumbling across a mugging victim in New York City who turns out to be a being from the world of Elphame, student librarian Ruth Marlowe and her friends learn that the muggers stole a magical sword that changes mortals into grendel-like monsters.
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Used availability for Rosemary Edghill's The Sword of Maiden's Tears
September 1994 : USA Mass Market Paperback